A fuel rail with enhanced design flexibility

Abstract

The present invention relates to a fuel rail (100) with a cylindrical tube hole (10) extending along a first central axis (A1). At a first end (1), the fuel rail (100) comprises a sealing plug housing (11). At a second end (2) distal to said first end (1), the fuel rail (100) comprises a tip connection (12). The tip connection (12) has a cylindrical geometry that extends along a second central axis (A2). The second central axis (A2) is eccentric according to the first central axis (A1). The tip connection (12) can be a fuel port. The present invention further proposes a method that enables the formation of such fuel rail (100).

Description

[0001] SPECIFICATION

[0002] A FUEL RAIL WITH ENHANCED DESIGN FLEXIBILITY

[0003] Technical Field of the Invention

[0004] The present invention relates to fuel rails for fuel distribution to fuel injectors used in combustion engines. In particular, the present invention relates to constructional details of fuel rails.

[0005] Background of the Invention

[0006] Fuel rails for fuel distribution to multiple fuel injectors are typical components of high- pressure fuel injection systems. Fuel rails can be obtained by forging and machining of stainless steel.

[0007] Forged fuel rails have advantages in terms of strength compared to soldered or brazed fuel rails and thus tend to allow higher injection pressures. Forged, monolithic (i.e., one-piece) fuel rails usually offer a lower extent of design flexibility compared to brazed rails. The forging process bears physical limits in forming of the forging material. On the other hand, a sufficient extent of accessibility from the outside for all machining operations must be available during machining.

[0008] However, in order to save on modification costs and new tests, industrial customers that seek for a new engine generation or a model upgrade are often reluctant to adapt the entire cylinder head to a forged rail. Therefore, it is desired to find solutions that preserve the advantages of lower cost and higher strength of forged rails over soldered rails, while increasing design flexibility.

[0009] Summary of the Invention

[0010] Primary object of the present invention is to overcome the above-mentioned shortcomings of the prior art. Another object of the present invention is to propose a solution for enabling replacement of a fuel rail that is designed in accordance with dimensional limitations of an engine, with a new fuel rail that is different in size and weight. A further object of the present invention is to propose a solution for enabling replacement of a fuel rail that is designed in accordance with dimensional limitations of an engine, with a new fuel rail that is more compact by having a smaller size and weight. A further object of the present invention is to decrease the costs in relation with fuel rails. Another object of the present invention is to provide facility and flexibility during using the drilling tools without changing the fixed position of the fuel rail during drilling the bores or channels of the fuel rail.

[0011] To this end, the present application proposes an elongate fuel rail with a cylindrical tube hole extending along a first central axis. At a first end, the fuel rail comprises a sealing plug housing. At a second end that is distal to said first end, the fuel rail comprises a tip connection; for instance, a fuel port. Here, the tip connection has a cylindrical geometry extending along a second central axis that is eccentric according to the first central axis of the tube hole.

[0012] In a possible embodiment, a first radial distance between an injector cup and the first central axis can be shorter than a second radial distance between said injector cup and the second central axis. Thus, a radially compact fuel injector is enabled.

[0013] In a possible embodiment, the second central axis of the tip connection can be parallel to the first central axis of the tube hole.

[0014] In a possible embodiment, the fuel rail can further comprise a plurality of side ports that are transversely distributed in-between the first end and second end, in hydraulic communication with the tube hole. The side ports can include injector cups.

[0015] In a possible embodiment, the tip connection can be in hydraulic communication with the tube hole through a bore extending along a bore axis that is eccentric according to the first central axis of the tube hole and / or with regard to the second central axis of the tip connection. This feature corresponds to an increased flexibility when selecting a shortest distance to be drilled / machined at forming the bore. In a possible embodiment, the fuel rail according to the present invention can be considered a forged fuel rail.

[0016] The present invention further proposes a method for production of such fuel rail. The method includes the following steps: a) forging an elongate body that is suitable for being shaped into a fuel rail; b) at a first end of the forged body, forming a sealing plug housing by machining a first cylindrical cavity along a first central axis; c) starting from the first cylindrical cavity, forming a tube hole by machining a second cylindrical cavity along the first central axis, towards a second end distal to the first end of the forged body; d) at the second end of the forged body, forming a tip connection by machining a third cylindrical cavity along a second central axis that is offset with respect to the first central axis; e) starting from the second cylindrical cavity, forming a bore by machining a fourth cylindrical cavity to constitute hydraulic communication between the tube hole and the tip connection.

[0017] In a possible variation, the method includes arrangement of that the fourth cylindrical cavity extends along a bore axis, that is eccentric according to the first central axis and / or with regard to second central axis.

[0018] Brief Description of Figures

[0019] 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.

[0020] Fig.l shows a longitudinal section view along the first central axis of an exemplary fuel rail according to the present application. The fuel rail includes a tip connection (e.g., high- pressure connection housing, such as a fuel port) with a second central axis that is offset and parallel to the first central axis. The first central axis is the central axis of the tube hole, whereas the second central axis is the central axis of the tip connection.

[0021] Fig.2 is a detail from Fig.l, corresponding to a first end of the fuel rail, showing the vicinity of the exemplary sealing plug housing.

[0022] Fig.3 is a detail from Fig.l, corresponding to a second end of the fuel rail, showing the vicinity of the exemplary tip connection.

[0023] Detailed Description of the Invention

[0024] Referring to the figures described above, the present application proposes an elongate fuel rail (100) with a cylindrical tube hole (10) that extends along a first central axis (Al) (i.e., central axis of cylindrical geometry of the tube hole (10)). At a first end (1) of the fuel rail (100), the fuel rail (100) comprises a sealing plug housing (11). At a second end (2) that is distal to said first end (1), the fuel rail (100) comprises a tip connection (12). The tip connection (12) can be a fuel port.

[0025] The tip connection (12) has a cylindrical geometry that extends along a second central axis (A2). The second central axis (A2) (i.e., central axis of cylindrical geometry of the tip connection (12)) is eccentric according to the first central axis (Al). In other words, the first central axis (Al) of the tube hole (10) and the second central axis (A2) of the tip connection (12) do not overlap with each other. It is thus enabled that a prior art fuel rail designed in accordance with dimensional limitations of a combustion motor vehicle, can be replaced with a fuel rail (100) according to the present invention, that is different in size and weight of the prior art fuel rail. In such replacement that is enabled within the context of the present invention, dimensional compatibility issues are inherently avoided in engaging with predetermined loci of fluid connections such as fuel supply and fuel injectors.

[0026] For instance, the present invention enables a compact fuel rail (100). In such fuel rail (100), a first radial distance between an injector cup and the first central axis (Al) can be shorter than a second radial distance between said injector cup and the second central axis (A2). Thus, a bulkier prior art fuel rail can be replaced with a fuel rail (100) that is more compact (less bulky) when compared to such prior art fuel rail. Inherently, the material costs, weight and total costs are reduced with the fuel rail (100) according to the present invention.

[0027] The fuel rail (100) described in the present application can be considered as a monolithic, forged body.

[0028] In a possible embodiment of the fuel rail (100), the second central axis (A2) of the tip connection (12) is parallel to the first central axis (Al) of the tube hole (10).

[0029] The fuel rail (100) can be considered as further comprising a plurality of side ports (13) that are transversely distributed in-between the first end (1) and the second end (2), in fluid flow communication with the tube hole (10). The fluid flow communication between the tube hole (10) and respective side ports (13) can be arranged via respective cross bores. The side ports (13) can be, e.g., injector cups.

[0030] The tip connection (12) can be considered inherently in fluid flow communication with the tube hole (10). For instance, the said fluid flow communication between the tip connection (12) and the tube hole (10) can be constituted through a bore (14).

[0031] In a possible embodiment, the bore (14) extends along a bore axis (A3) that can be eccentric according to the first central axis (Al) of the tube hole (10). In a further possible embodiment, the bore axis (A3) can be eccentric according to the second central axis (A2) of the tip connection (12). In a further possible embodiment, the bore axis (A3) can be eccentric according to the first central axis (Al) of the tube hole (10) and also with regard to the second central axis (A2) of the tip connection (12).

[0032] The fuel rail (100) according to the present invention can be, in particular, formed by forging. Such fuel rail (100) can be considered a forged fuel rail.

[0033] An exemplary method for production of the fuel rail (100) according to the present invention includes the following steps: a) forging an elongate body that is suitable for being shaped into a fuel rail (100); b) at a first end (1) of the forged body, forming a sealing plug housing (11) by machining a first cylindrical cavity along a first central axis (Al); c) starting from the first cylindrical cavity, forming a tube hole (10) by machining a second cylindrical cavity along the first central axis (Al), towards a second end (2) distal to the first end (1) of the forged body; d) at the second end (2) of the forged body, forming a tip connection (12) by machining a third cylindrical cavity along a second central axis (A2) that is offset with respect to the first central axis (Al); e) starting from the second cylindrical cavity, forming a bore (14) by machining (e.g., drilling) a fourth cylindrical cavity to constitute hydraulic communication between the tube hole (10) and the tip connection (12). The fourth cylindrical cavity can be considered to extend along a bore axis (A3), that can be parallel or offset to one or both of the first central axis (Al) and second central axis (A2).

[0034] In the step (c), the machining of the tube hole (10) can be considered to be performed such that a (not yet machined, or non-cavity) distance is maintained inside the body, between the second end (2) and the tube hole (10). Said distance is reserved for formation of a tip connection (12) in step (d), and for formation of the bore (14) for hydraulically connecting the tip connection (12) with the tube hole (10) in step (e).

[0035] In the step (d), the term "offset" can be considered to indicate that the first central axis (Al) and second central axis (A2) do not overlap with each other. For instance, the first central axis (Al) and second central axis (A2) can extend parallel to each other.

[0036] The features and effects proposed in the present application can also be formulated as follows:

[0037] Within the context of the present application, the term "eccentric" can be considered synonym to "offset" when evaluating relative positions of substantially cylindrical cavities that have non-overlapping and loci of respective central axes. Said loci of respective central axes can be substantially parallel to each other. Within the context of the present application, the tube hole (10) can also be named as "deep hole".

[0038] The fuel port can be considered as an axial connection. The term "axial connection" refers to a connection to be disposed at an end or tip of the fuel rail (100), and that extends in a direction parallel to the main central axis of the respective tube hole (10). Therefore, within the present description, the tip connection (12) can be also referred to as "axial connection".

[0039] The solution presented here enables that an axial connection such as a sensor connection or high-pressure connection (here: tip connection (12), in particular, fuel supply connection) to be attached eccentrically with regard to the main first central axis (Al) of a tube hole (10). Thus, the design flexibility of forged fuel rail (100) is increased without compromising the advantages of forged fuel rails, particularly in comparison with brazed fuel rails. The implementation of a tip connection (12) as described in the present application, does not increase production costs of the fuel rail (100).

[0040] On the other hand, the present solution further enables a maximized homogeneity in mass distribution in the fuel rail (100); thereby increases the forgeability and reduces the use of materials. Fig.l shows a cross-section through a fuel rail (100) with an offset between the axial high-pressure connection (tip connection (12)) and the deep-hole bore (tube hole (10)). It can also be seen that if the first central axis (Al) would overlap the second central axis (A2), radial distance between the tube hole (10) and the side ports (13) would be longer.

[0041] Thus, for example, the locus of the first central axis (Al) can be shifted more towards the side ports (13) while the position of the tip connection (12) remains unchanged. As a result, the center of gravity of the forged body (fuel rail (100)) is also shifted towards the side ports (13); inevitably resulting in a reduction of material usage in production of the fuel rail (100). In other words, a fuel rail with pre-determined dimensional limitations with regard to loci for axial connection(s) and side ports (13) such as injector cups, can be replaced with a fuel rail (100) with a first central axis (Al) that has a different radial distance to the side ports (13). Considering that the side ports (13) are brought into fluid communication with the tube hole (10) through (substantially-) radial connections such as cross holes that can be formed by drilling; the present invention enables shortening of said radial distance, thus facilitating the production of the fuel rail (100). This aspect also corresponds to a design flexibility, which further minimizes the production costs.

[0042] When in use, the side ports (13) can be occupied by, e.g., injector cups, sensor connections and various high-pressure connections that can be employed with the fuel rail (100).

[0043] In order to implement eccentric tip connection (12) with regard to the tube hole (10), clamping points for drilling or machining of the tube hole (10) can be outside of the around the tip connection (12) that is to be formed.

[0044] The clamping points for drilling and, if necessary, for radial machining of the tube hole (10) are typically cylindrical surfaces or chamfers with e.g., 45 degrees angles with respect to the planned first central axis (Al). Here, the clamping surfaces or chamfers can be considered as centric to the first central axis (Al) but eccentric to the second central axis (A2).

[0045] Possible surfaces and chamfers for clamping are highlighted with bold dashed lines in Fig.2 and Fig.3 respectively, for both ends of the fuel rail (100). In order to arrange that the bore (14) opens more centrally to the tube hole (10), the bore (14) can be formed offset with respect to the second central axis (A2) (see Fig.3).

[0046] Reference signs

[0047] 1 first end

[0048] 2 second end

[0049] 10 tube hole 11 sealing plug housing

[0050] 12 tip connection

[0051] 13 side port

[0052] 14 bore

[0053] 100 fuel rail Al first central axis

[0054] A2 second central axis

[0055] A3 bore axis

Claims

Claims An elongate fuel rail (100) with a cylindrical tube hole (10) extending along a first central axis (Al); at a first end (1), the fuel rail (100) comprises a sealing plug housing (11); at a second end (2) distal to said first end (1), the fuel rail (100) comprises a tip connection (12); wherein the tip connection (12) has a cylindrical geometry extending along a second central axis (A2) that is eccentric according to the first central axis (Al) of the tube hole (10). The fuel rail (100) according to claim 1, wherein a first radial distance between an injector cup and the first central axis (Al) is shorter than a second radial distance between said injector cup and the second central axis (A2). The fuel rail (100) according to any of claims 1 or 2, wherein the tip connection (12) is a fuel port. The fuel rail (100) according to any of claims 1 to 3, wherein the second central axis (A2) of the tip connection (12) is parallel to the first central axis (Al) of the tube hole (10). The fuel rail (100) according to any of claims 1 to 4, further comprising a plurality of side ports (13) transversely distributed in-between the first end (1) and the second end (2), in fluid flow communication with the tube hole (10). The fuel rail (100) according to any of claims 1 to 5, wherein the tip connection (12) is in fluid flow communication with the tube hole (10) through a bore (14) that extends along a bore axis (A3) that is eccentric according to the first central axis (Al) of the tube hole (10) and / or with regard to the second central axis (A2) of the tip connection (12). The fuel rail (100) according to any of claims 1 to 6, wherein the fuel rail (100) is formed by forging. A method for production of a fuel rail (100) wherein the method includes the following steps: a) forging an elongate body for being shaped into a fuel rail (100);b) at a first end (1) of the forged body, forming a sealing plug housing (11) by machining a first cylindrical cavity along a first central axis (Al); c) starting from the first cylindrical cavity, forming a tube hole (10) by machining a second cylindrical cavity along the first central axis (Al), towards a second end (2) distal to the first end (1) of the forged body; d) at the second end (2) of the forged body, forming a tip connection (12) by machining a third cylindrical cavity along a second central axis (A2) that is offset with respect to the first central axis (Al); e) starting from the second cylindrical cavity, forming a bore (14) by machining a fourth cylindrical cavity to constitute hydraulic communication between the tube hole (10) and the tip connection (12). The method according to claim 8, wherein the method includes arrangement of that the fourth cylindrical cavity extends along a bore axis (A3), that is eccentric according to the first central axis (Al) and / or with regard to second central axis

Images