EP4532920A1

EP4532920A1 - A fuel rail and a simple method for preparation of the same

Info

Publication number: EP4532920A1
Application number: EP23721949.8A
Authority: EP
Inventors: Semih BILIR
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2022-04-28
Filing date: 2023-04-28
Publication date: 2025-04-09

Abstract

The present invention relates to a fuel rail (1000) that comprises a tube (10) with a tube hole (11). The fuel rail (1000) further comprises and a plurality of injector cups (20) in fluid flow communication with the tube hole (11) via a respective plurality of T-shaped cross bores that include a first bore (B1) and a second bore (B2). The first bore (B1) extends from the tube hole (11) towards a front face (22) of a respective injector cup (20). Said front face (22) is distal to the tube hole (11) with regard to a central axis of the first bore (B1). The second bore (B2) is arranged to provide fluid flow communication from the first bore (B1) to an inner volume (21) of the injector cup (20). The first bore (B1) is provided with a plug (60) at a distal end of the first bore (B1) with regard to the tube hole (11). The plug (60) is fixed to the first bore (B1) by pressing of the plug (60) into the first bore (B1) in an axial direction along the first bore (B1) towards the tube hole (11) at an instance of a capacitor discharge that is applied onto the plug (60). The present invention further proposes a method for obtaining such fuel injector (1).

Description

SPECIFICATION

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 preparation of 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.

Summary

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 a fuel rail that comprises a tube with a tube hole. The fuel rail further comprises 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 is 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. The plug is fixed to the first bore by pressing of the plug into the first bore in an axial direction along the first bore towards the tube hole at an instance of a capacitor discharge that is applied onto the plug. Such fixing can be considered as capacitor discharge press-in welding, and provides an easy and low-cost sealing that is sufficient under high-pressure conditions in fuel rails, without necessitating any further measures for sealing.

In a possible embodiment, the first bore can include a plug housing at said distal end of the first bore with regard to the tube hole, for receiving the plug; such that, around a longitudinal axis of the first bore, a radial width at the plug housing has a greater value when compared to a radial width of the first bore at a tube hole side end thereof. In such case, the geometry of plug can be considered farther from being pin-like; in other words, a length (or height) per diameter value of the plug can be arranged to be rather low. This measure facilitates the manufacturing of the plug, e.g., by turning.

Prior to fixing, the diameter of the plug can be considered to be slightly larger than the diameter of the plug housing, thereby ensuring circumferential sealing upon the fixing.

In a possible embodiment, the plug and plug housing can have cylindrical geometries having respective heights along the central axis of the first bore, and the height of the plug can be smaller than the height of the plug housing. This allows a decreased materials costs when producing the plug, and decreases the final costs in preparing the fuel rail.

The present invention further proposes a method for obtaining a fuel rail that comprises a tube with a tube hole and a plurality of injector cups that have an inner volume in fluid flow communication with the tube hole via a T-shaped cross bore that includes a first bore and a second bore transverse to the first bore. The method includes the following steps: a) drilling a front face of a respective injector cup to form the first bore that opens to the tube hole; b) drilling from the inner volume of the injector cup to form a second bore that constitutes fluid flow communication between the first bore and the inner volume; and c) sealing a distal end of the first bore with respect to the tube hole by fixing a plug at said distal end of the first bore.

It is not mandatory to perform the steps (a) to (c) consecutively in the order given above. Yet, in an advantageous option, the steps (a)-(c) can be consecutively performed in the order given above. In such case, the fixing step starts after termination of the drilling steps; thereby simplifying the overall process for preparation of the fuel rail.

Said fixing is performed by pressing of the plug into the first bore in an axial direction along the first bore towards the tube hole at an instance of a capacitor discharge that is applied onto the plug. So, within the context of the present application, said fixing is performed using capacitor discharge press-in welding of the plug. So, the above-mentioned advantages of the capacitor discharge press-in welding are implemented into the present method.

After the step (a), a possible variation of the method includes formation of a plug housing for receiving the plug; such that, around a longitudinal axis of the first bore, a radial width at the plug housing has a greater value when compared to the radial width of the first bore at a tube hole side end thereof.

A possible variation of the proposed method includes the arrangement of that the plug and plug housing have cylindrical geometries with respective heights along the longitudinal axis of the first bore when aligned with each other, such that the plug housing has a greater height when compared to that of the plug.

The present application further proposes the use of capacitor discharge press-in welding in preparation of a fuel rail comprising a T-shaped cross bore that provides fluid flow communication between a tube hole and an inner volume of an injector cup. Here, said use is performed at sealing of an end of the cross bore that opens to a front face of the injector cup distal to the tube hole, with a plug.

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.l represents a perspective view of an exemplary fuel rail, wherein fuel injectors and sensor are omitted.

Fig.2 represents a perspective view of another exemplary forged fuel rail according to the present application, wherein fuel injectors and sensor are omitted.

Fig.3 is a side view of the fuel rail shown in Fig.2.

Fig.4 is the A-A section from the Fig.3.

Fig.5 is perspective view of a plug for use in sealing of the plug housing shown in Fig.4.

Fig.6 is the section shown in Fig.4, wherein the plug housing is provided with the plug shown in Fig.5.

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 (30) 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, 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). 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.

In a possible variation, the fixing method is capacitor discharge press-in welding. Capacitor discharge press-in welding is different from laser welding and capacitor discharge welding that require relatively higher investment costs. Capacitor discharge press-in welding is a comparatively simple process and requires a decreased extent of investment costs.

Within the context of the present application, capacitor discharge press-in welding can be defined in that it includes pressing of the plug (60) into the first bore (Bl) in an axial direction along the first bore (Bl) towards the tube hole (11) at an instance of a capacitor discharge that is applied onto the plug (60).

The first bore (Bl) can include a plug housing (61) at said front face side end, for receiving the plug (60). Around a longitudinal axis of the first bore (Bl), a radial width at the plug housing (61) can have a greater value when compared to the radial width of the first bore (Bl) at a tube hole side end thereof. In such case, the plug (60) is pressed into the plug housing (61), towards the tube hole (11). Although not a mandatory technical constraint, throughout the present specification, the longitudinal axis of the first bore (Bl) can be considered to coincide with the injector cup axis (Ac). The longitudinal axis of the first bore (Bl) can be considered as plug axis (Ap). The plug (60) and plug housing (61) can both be considered to have cylindrical geometries with respective heights, diameters (thus, radii) and central axes orthogonal to respective cylinder bases. Here, the heights can be defined as vertical distances between bases. The diameters correspond to radial widths around the respective central axes of the respective cylindrical geometries of the plug (60) and plug housing (61).

Prior to the capacitor discharge press-in welding, the height of the plug (60) can be smaller than the height of the plug housing (61). In such case, the height of the plug (60) remains smaller than the height of the plug housing (61) upon the fixing of the plug (60). So, the sealing of the cross bore is performed with a minimal use of material that form the plug (60).

Prior to the capacitor discharge press-in welding, the radius of the plug (60) can be greater than the radius of the plug housing (61). The difference between the radii of the plug (60) and the plug housing (61) can be named as "interference extent". Considering that the mechanical pressure force exerted onto the plug (60) at capacitor discharge press-in welding locally increases the diameter of the plug (60) at portions outside the plug housing (61); the interference extent can also be defined as a half of the difference between a diameter of the plug housing (61) and a local radial width or local diameter of the plug (60) measurable outside the front face (22) upon the completion of the fixing of the plug (60).

At the capacitor discharge press-in welding, the plug (60) is circumferentially welded to the plug housing (61) around the central axis of the plug (60), at a depth along said central axis of the plug (60). Said depth can be named as "welding length". Here, since the welding is performed by capacitor discharge press-in welding, it is not necessary to employ an auxiliary welding material.

The presence of the interference extent and welding length can be determined by visual inspection; for instance, by cutting the injector cup (20) along the longitudinal axis of the first bore (Bl). The presence of the interference extent and welding length can be considered as a proof of that the fixing of the plug (60) is performed by capacitor discharge press-in welding. In other words, according to the information provided above, the present invention proposes a fuel rail (1000) that comprises a tube (10) with a tube hole (11). The fuel rail (1000) further comprises and a plurality of injector cups (20) in fluid flow communication with the tube hole (11) via a respective plurality of T-shaped cross bores that include a first bore (Bl) and a second bore (B2). The first bore (Bl) extends from the tube hole (11) towards a front face (22) of a respective injector cup (20). Said front face (22) is distal to the tube hole (11) with regard to a central axis of the first bore (Bl). The second bore (B2) is arranged to provide fluid flow communication from the first bore (Bl) to an inner volume (21) of the injector cup (20). The first bore (Bl) is provided with a plug (60) at a distal end of the first bore (Bl) with regard to the tube hole (11). The plug (60) is fixed to the first bore (Bl) by pressing of the plug (60) into the first bore (Bl) in an axial direction along the first bore (Bl) towards the tube hole (11) at an instance of a capacitor discharge that is applied onto the plug (60).

In a possible embodiment, the first bore (Bl) can include a plug housing (61) at said distal end of the first bore (Bl) with regard to the tube hole (11), for receiving the plug (60); such that, around a longitudinal axis of the first bore (Bl), a radial width at the plug housing (61) has a greater value when compared to a radial width of the first bore (Bl) at a tube hole side end thereof.

In a possible embodiment, the plug (60) and plug housing (61) can have cylindrical geometries having respective heights along the central axis of the first bore (Bl), and the height of the plug (60) can be smaller than the height of the plug housing (61).

The present invention further proposes a method for obtaining a fuel rail (1000) that comprises a tube (10) with a tube hole (11) and a plurality of injector cups (20) that have an inner volume (21) in fluid flow communication with the tube hole (11) via a T-shaped cross bore that includes a first bore (Bl) and a second bore (B2) transverse to the first bore (Bl). The method includes the following steps: a) drilling a front face (22) of a respective injector cup (20) to form the first bore (Bl) that opens to the tube hole (11); b) drilling from the inner volume (21) of the injector cup (20) to form a second bore (B2) that constitutes fluid flow communication between the first bore (Bl) and the inner volume (21); and c) sealing a distal end of the first bore (Bl) with respect to the tube hole (11) by fixing a plug (60) at said distal end of the first bore (Bl).

It is not mandatory to perform the steps (a) to (c) consecutively in the order given above.

Said fixing is performed by pressing of the plug (60) into the first bore (Bl) in an axial direction along the first bore (Bl) towards the tube hole (11) at an instance of a capacitor discharge that is applied onto the plug (60). So, within the context of the present application, said fixing is performed using capacitor discharge press-in welding of the plug (60).

After the step (a), a possible variation of the method includes formation of a plug housing (61) for receiving the plug (60); such that, around a longitudinal axis of the first bore (Bl), a radial width at the plug housing (61) has a greater value when compared to the radial width of the first bore (Bl) at a tube hole side end thereof.

A possible variation of the proposed method includes the arrangement of that the plug (60) and plug housing (61) have cylindrical geometries with respective heights along the longitudinal axis of the first bore (Bl) when aligned with each other, such that the plug housing (61) has a greater height when compared to that of the plug (60).

The present application further proposes the use of capacitor discharge press-in welding in preparation of a fuel rail (1000) comprising a T-shaped cross bore that provides fluid flow communication between a tube hole (11) and an inner volume (21) of an injector cup (20). Here, said use is performed at sealing of an end of the cross bore that opens to a front face (22) of the injector cup (20) distal to the tube hole (11), with a plug (60). 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 1000 fuel rail

Ac injector cup axis

Ap plug axis

At tube axis

Bl first bore B2 second bore

Claims

1. A fuel rail (1000) that comprises a tube (10) with a tube hole (11) and a plurality of injector cups (20) in fluid flow communication with the tube hole (11) via a respective plurality of T-shaped cross bores that include a first bore (Bl) and a second bore (B2); the first bore (Bl) extends from the tube hole (11) towards a front face (22) of a respective injector cup (20), said front face (22) being distal to the tube hole (11) with regard to a central axis of the first bore (Bl), and the second bore (B2) is arranged to provide fluid flow communication from the first bore (Bl) to an inner volume (21) of the injector cup (20); the first bore (Bl) is provided with a plug (60) at a distal end of the first bore (Bl) with regard to the tube hole (11); wherein the plug (60) is fixed to the first bore (Bl) by pressing of the plug (60) into the first bore (Bl) in an axial direction along the first bore (Bl) towards the tube hole (11) at an instance of a capacitor discharge that is applied onto the plug (60).

2. The fuel rail according to claim 1, wherein the first bore (Bl) includes a plug housing (61) at said distal end of the first bore (Bl) with regard to the tube hole (11), for receiving the plug (60); such that, around a longitudinal axis of the first bore (Bl), a radial width at the plug housing (61) has a greater value when compared to a radial width of the first bore (Bl) at a tube hole side end thereof.

3. The fuel rail according to claim 2, wherein the plug (60) and plug housing (61) have cylindrical geometries having 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).

4. A method for obtaining a fuel rail (1000) that comprises a tube (10) with a tube hole (11) and a plurality of injector cups (20) that have an inner volume (21) in fluid flow communication with the tube hole (11) via a T-shaped cross bore that includes a first bore (Bl) and a second bore (B2) transverse to the first bore (Bl), the method includes the following steps: a) drilling a front face (22) of a respective injector cup (20) to form the first bore (Bl) that opens to the tube hole (11); b) drilling from the inner volume (21) of the injector cup (20) to form a second bore (B2) that constitutes fluid flow communication between the first bore (Bl) and the inner volume (21); and c) sealing a distal end of the first bore (Bl) with respect to the tube hole (11) by fixing a plug (60) at said distal end of the first bore (Bl); wherein said fixing is performed by pressing of the plug (60) into the first bore (Bl) in an axial direction along the first bore (Bl) towards the tube hole (11) at an instance of a capacitor discharge that is applied onto the plug (60). The method according to claim 4, wherein, after the step (a), the method includes formation of a plug housing (61) for receiving the plug (60); such that, around a longitudinal axis of the first bore (Bl), a radial width at the plug housing (61) has a greater value when compared to the radial width of the first bore (Bl) at a tube hole side end thereof. The method according to claim 5, wherein the method includes arranging that the plug (60) and plug housing (61) have cylindrical geometries having respective heights along the longitudinal axis of the first bore (Bl) when aligned with each other, such that the plug housing (61) has a greater height when compared to that of the plug (60). Use of capacitor discharge press-in welding in preparation of a fuel rail (1000) comprising a T-shaped cross bore that provides fluid flow communication between a tube hole (11) and an inner volume (21) of an injector cup (20); wherein said use is performed at sealing of an end of the cross bore that opens to a front face (22) of the injector cup (20) distal to the tube hole (11), with a plug (60).