Fuel rail with enhanced sealing

Abstract

The invention relates to a fuel rail (100), the cylindrical tube bore (10) of which extends along a central axis (A). At the first end (1), the fuel rail (100) comprises a sealing plug housing for receiving the plug (11) to seal the first end (1) of the bore (10). The invention also proposes a method which enables the formation of a fuel rail (100) with an end plug (11) with enhanced sealing by friction welding or friction brazing.

Description

Field of the Invention

[0001] The present invention relates to a fuel rail for distributing fuel to a fuel injector used in an internal combustion engine. In particular, the present invention relates to the structural details of the fuel rail. Background Art

[0002] A rail for distributing fuel to a plurality of fuel injectors is a typical component of a high-pressure fuel injection system. The fuel rail can be obtained by forging and machining stainless steel.

[0003] Compared with welded or brazed rails, forged rails have an advantage in terms of strength and thus tend to allow higher injection pressures. Compared with brazed rails, forged integral (i.e., one-piece) fuel rails generally offer lower design flexibility. The forging process has physical limitations in the formation of the forged material.

[0004] EP1826396A1 discloses an exemplary prior art fuel rail for an internal combustion engine. The fuel rail extends along a central axis. The fuel rail has a fuel port at one end and also has a plurality of side ports distributed transversely along the fuel rail.

[0005] In the prior art, the fuel rail may include an end connection portion in hydraulic communication with a pipe hole and an end plug remote from the end connection portion. The end plug and the first end of the fuel rail have mating threads. The end connection can be a high-pressure connection housing, such as a fuel port. During assembly, the threads are subject to wear or abrasion, which affects the geometric accuracy between the mating threads. Threads without precise geometry can form a flow path for pressurized fuel in the pipe hole, resulting in fuel leakage around the end plug. This possibility poses a risk of damage, especially when the fuel is gasoline. Achieving the geometric accuracy of the threads is costly.

[0006] A sealing device made of rubber can be used, but rubber cannot be considered completely safe because it is prone to tearing under high fuel pressure.

[0007] Another method is to use a conventional welding method to weld the end plug to the inside of the first end. However, welding in an internal space is difficult, especially in the case of opposite angles.

[0008] There is a desire to find a simple and low-cost solution to eliminate potential fuel leakage around the end plug used in the fuel rail. Summary of the Invention

[0009] The main object of the present invention is to overcome the above-mentioned disadvantages of the prior art. Another object of the present invention is to propose a simple and low-cost solution for sealing the distal end of the fuel rail relative to the corresponding fuel port.

[0010] To this end, the present application proposes a bar-shaped fuel rail, the cylindrical tube holes of which extend along the central circumferential axis. At the first end, the fuel rail includes a sealing plug housing provided with an end plug. The first end and the end plug are made of at least one first metal material. The fuel rail according to the present disclosure has two main options, which are hereby introduced together in one inventive concept. Both options are easy to apply quickly and thus are low-cost.

[0011] In a first alternative of the main context of the present application, the first end and the end plug are fixed relative to each other by friction welding. Friction welding provides a seal around the central axis by filling the potential flow path around the end plug with temporarily softened first metal material from the fuel rail or from the end plug.

[0012] In a second alternative of the main context of the present application, a second metal material is provided around the central axis between the first end and the end plug. The melting point of the second metal material is lower than the melting point of at least one of the first metal materials of the fuel rail or the end plug.

[0013] In the second option, the first end and the end plug are fixed relative to each other by friction brazing. Friction brazing provides a seal around the central axis by filling the potential flow path around the end plug with temporarily softened second metal material. Although providing the second metal material involves a further step, friction brazing provides convenient softening because the second metal material is easier to soften than the first metal material, and thus there is a possibility of reducing production costs.

[0014] In the context of the present application, the softening of the metal material can also be referred to as plasticization, so the softened metal material can undergo plastic deformation.

[0015] Since the end plug itself has a cylindrical geometry extending along the central axis, friction welding and friction brazing can also be referred to as rotary friction welding and rotary friction brazing, respectively.

[0016] The first metal material can be stainless steel. Stainless steel is suitable for forming the fuel rail and the end plug.

[0017] In the case of friction brazing, the second metal material can contain copper. Copper is easy to form and can also be used in a paste form. In other words, it is easy and low-cost to form an annular body (such as a sheet) from the second metal material to obtain the fuel rail according to the second alternative. Friction-induced softening does require a relatively low temperature. Therefore, copper as the second metal material can reduce the residual stress in the friction heating zone. This will shorten the process duration because the requirement for additional heat input is minimized or even eliminated.

[0018] The fuel rail may include an end connection portion at a second end located away from the first end. The end connection portion may be adapted to serve as a fuel port. The fuel rail may further include a plurality of side ports that are laterally distributed between the first end and the second end and are in hydraulic communication with the tube bore.

[0019] The fuel rail may be formed by forging.

[0020] In accordance with the above instructions, the present application also proposes a method for producing a fuel rail.

[0021] A first alternative of the method includes the following steps, and thus the method involves friction welding:

[0022] a) Providing a cylindrical tube bore extending along a central axis in the fuel rail; providing a seal plug housing for the first end of the fuel rail, the seal plug housing being provided with an end plug; forming the first end and the end plug from at least one first metal material;

[0023] b) Aligning and pressing the end plug into the first end along the central axis;

[0024] c) Rotating the end plug relative to the first end about the central axis until at least one first metal material softens for friction welding;

[0025] d) Stopping the rotation of the end plug relative to the first end.

[0026] A second alternative of the method according to the present application includes the following steps, and thus the method involves friction brazing:

[0027] i. Providing a cylindrical tube bore extending along a central axis in the fuel rail; providing a seal plug housing for the first end of the fuel rail, the seal plug housing being provided with an end plug; forming the first end and the end plug from at least one first metal material;

[0028] ii. Providing an annular sheet of a second metal material having a melting point lower than that of at least one first metal material of the first end and the end plug;

[0029] iii. Aligning and pressing the end plug into the first end along the central axis;

[0030] iv. Rotating the end plug relative to the first end about the central axis until the second metal material softens for friction brazing;

[0031] v. Stopping the rotation of the end plug relative to the first end.

[0032] The method may include providing at least one annular gap around the end plug about the central axis before step i or step ii. The annular gap is substantially filled with the softened (first or second) metal material.

[0033] According to the above description:

[0034] - The first or second alternative of the method may include the first metal material being set as stainless steel. When implemented by friction brazing, the method may further include the second metal material being set to include copper.

[0035] - The method may include providing an end connection portion at a second end of the fuel rail remote from the first end, the end connection portion being adapted to serve as a fuel port.

[0036] - The method may include providing a plurality of side ports for the fuel rail that are laterally distributed between the first end and the second end (2), the plurality of side ports being in hydraulic communication with the tube bore.

[0037] - The method may include forming the fuel rail by forging.

[0038] The present application also proposes using friction welding or friction brazing to fix an end plug to the first end of the fuel rail. According to the above description, using friction welding or friction brazing eliminates the possibility of fuel leakage around the end plug without incurring high costs. Description of the Drawings

[0039] The drawings (a brief description of which is hereby provided) are only for providing a better understanding of the present invention and are not therefore used to limit the scope of protection or to interpret the scope in the absence of the specification.

[0040] Figure 1a A longitudinal sectional view along the central axis of a fuel rail of an exemplary prior art is shown. The fuel rail includes an end connection portion (e.g., a high-pressure connection portion housing, e.g., a fuel port) in hydraulic communication with the tube bore and an end plug remote from the end connection portion.

[0041] Figure 1b is taken from Figure 1a A close-up view of detail J. The end plug is attached by mating threads.

[0042] Figure 2a A longitudinal sectional view along the central axis of an exemplary fuel rail embodiment according to the present application is shown.

[0043] Figure 2b is taken from Figure 2a A close-up view of detail K. Here, the end plug is fixed by rotary friction welding.

[0044] Figure 3a A longitudinal sectional view along the central axis of another exemplary fuel rail embodiment according to the present application is shown.

[0045] Figure 3b is taken from Figure 3a A close-up view of detail M. Here, the end plug is fixed by rotary friction brazing. Detailed implementation mode

[0046] Referring to the above-mentioned drawings, the present application proposes a bar-shaped fuel rail 100, which has a cylindrical tube hole 10 extending along the central axis A. The central axis A can be considered to correspond to the main axis of the cylindrical geometry of the tube hole 10.

[0047] At the first end 1 of the fuel rail 100, the fuel rail 100 includes a sealing plug housing for receiving an end plug 11 to seal the tube hole 10. That is, when assembling the fuel rail 100, the first end 1 is sealed by the end plug 11.

[0048] Figure 1a A longitudinal sectional view of another exemplary prior art fuel rail 100 along the central axis A is shown. The fuel rail 100 may include an end connection portion 12 in hydraulic communication with the tube hole 10 and an end plug 11 remote from the end connection portion 12. The end plug 11 and the first end 1 have mating threads. The end connection portion 12 may be a high-pressure connection portion housing, such as a fuel port. Figure 1b is Figure 1a A close-up view of detail J in. The end plug 11 is attached to the first end 1 by mating threads. During assembly, the threads will wear or be damaged, which will affect the geometric accuracy between the mating threads. Threads without precise geometry can form a flow path for the pressurized fuel in the tube hole 10, causing the fuel rail 100 to leak around the end plug 11. This possibility poses a risk of damage, especially when the fuel is gasoline. Achieving the geometric accuracy of the threads is costly.

[0049] It can be considered that at least the first end 1, the sealing plug housing and the end plug 11 are made of at least one first metal material, for example, made of stainless steel. It can be further considered that a possible intermediate material can be provided between the sealing plug housing and the end plug 11 around the central axis A. The possible intermediate material can be a second metal material 20, which has a lower melting temperature compared to at least one first metal material forming the first end 1, the sealing plug housing and the end plug 11. For example, the second metal material 20 can be copper or include copper. The first metal material and the second metal material 20 can be considered to soften at a temperature of 60% of their respective melting temperatures (absolute). After softening, the corresponding materials can be deformed by applying forces in the first direction towards the second end and in the radial direction towards the inner wall of the first end of the fuel rail. Therefore, the corresponding materials tend to fill any flow path, thereby achieving sealing.

[0050] In the context of the present application, the sealing of the first end 1 is achieved by softening the first and / or second metal materials 20. Softening is achieved by increasing the local temperature value through friction.

[0051] In a first alternative of the method according to the invention, the end plug 11 is fixed to the first end 1 by rotary friction welding. Accordingly, the corresponding alternative of the method comprises the following steps:

[0052] a) Providing a fuel rail 100 with a first end 1 and an end plug 11 for fixing to the first end 1; the first end 1 and the end plug 11 are made of at least one first metallic material;

[0053] b) Aligning and pressing the end plug 11 against the first end 1 along the central axis A;

[0054] c) Rotating the end plug 11 relative to the first end 1 about the central axis A until at least one first metallic material softens;

[0055] d) Stopping the rotation of the end plug 11 relative to the first end 1.

[0056] After step d), when the temperature drops to a value below the softening temperature, the end plug 11 is permanently fixed to the first end 1. Accordingly, the fixing by rotary friction welding can be considered thorough.

[0057] In step c), the following application can be considered: one or both of the construction materials of the first end 1 and the end plug 11 reach the softening temperature. The softening temperature can be considered to correspond to 60% of the respective melting point. Accordingly, the softened material fills any possible flow paths around the end plug 11, thus achieving a seal around the central axis A.

[0058] In a second alternative of the method according to the present disclosure, a second metallic material 20 is provided around the end plug 11 about the central axis A.

[0059] The corresponding alternative of the method involves fixing the end plug 11 to the first end 1 by rotary friction brazing and comprises the following operations:

[0060] i. Providing a fuel rail 100 with a first end 1 and an end plug 11 for fixing to the first end 1; the first end 1 and the end plug 11 are made of at least one first metallic material;

[0061] ii. Providing an annular sheet of the second metallic material 20, the melting point of the second metallic material being lower than the melting point of at least one first metallic material of the first end 1 and the end plug 11;

[0062] iii. Aligning and pressing the end plug 11 against the first end 1 along the central axis A;

[0063] iv. Rotating the end plug 11 relative to the first end 1 about the central axis A until the second metallic material 20 softens;

[0064] v. Stopping the rotation of the end plug 11 relative to the first end 1.

[0065] When the temperature is reduced to below the softening temperature of the second metal material 20, the end plug 11 is permanently fixed to the first end 1; thus, the fixation by rotary friction brazing can be considered thorough.

[0066] In step ii, the amount of the second metal material 20 can be varied according to the geometry of the opposing surfaces of the first end 1 and the end plug 11. For example, a copper sheet of corresponding shape and dimensions obtained in step ii can be placed on one or both of the first end 1 and the end plug 11 and then fixed, for example, using laser welding. Then, the remaining steps can be applied. As an alternative, copper paste can be used instead of or together with the copper sheet.

[0067] In step iv, the following application can be considered: the second metal material 20 located between the first end 1 and the end plug 11 and surrounding the central axis A reaches the softening temperature. The softening temperature can be considered to correspond to 60% of the respective melting point. Thus, the softened second metal material 20 fills any possible flow paths around the end plug 11, thereby achieving a seal around the central axis A.

[0068] According to the present application, in the longitudinal section of the fuel rail 100, the fact that the end plug 11 is fixed to the first end 1 can be visually detected along the central axis A. If the second alternative of the method is implemented, the second metal material 20 different from the first metal material can also be visually observed, and the melting points of the first metal material and the second metal material 20 can be compared by observing the corresponding samples under a gradually increasing temperature program.

[0069] In both methods, before fixing the end plug 11 to the first end 1, at least one annular gap 30 surrounding the central axis A can be provided around the end plug 11; thereby allowing the softened metal material to radially migrate and fill the annular gap 30 in the respective penultimate step c or iv. The radial migration of the softened metal material can also be referred to as flash or burr.

[0070] Preferably, in the first and second alternatives of the method according to the present invention, the main body of the fuel rail 100 including the first end 1 remains stationary, thereby eliminating the balance loss associated with uneven weight distribution around the central axis A. Thus, the end plug 11 rotates relative to the first end 1. The rotation can be carried out at a speed of about 2000 rpm or higher; and the end plug 11 can approach the second end 2 along the central axis A simultaneously, for example, at a translational speed of 1 millimeter per second.

[0071] At a second end 2 remote from the first end 1, the fuel rail 100 can be considered to include an end connection portion 12, which can be a fuel port. The fuel rail 100 can include a plurality of side ports 13, which are laterally distributed between the first end 1 and the second end 2 and are in fluid communication with the tube hole 10. The fuel rail 100 can be formed by forging.

[0072] List of Reference Numerals

[0073] 1 First end

[0074] 2 Second end

[0075] 10 Tube hole

[0076] 11 End plug

[0077] 12 End connection portion

[0078] 13 Side port

[0079] 20 Second metal material

[0080] 30 Gap

[0081] 100 Fuel rail

[0082] A Central axis

Claims

1. A strip-shaped fuel rail (100) having a cylindrical tube hole (10) extending along a central axis (A); at a first end (1), the fuel rail (100) comprises a sealing plug housing provided with an end plug (11); the first end (1) and the end plug (11) are made of at least one first metal material; in, The first end (1) and the end plug (11) are fixed relative to each other by friction welding, or A second metal material (20) is arranged between the first end (1) and the end plug (11) around the central axis (A), the melting point of the second metal material (20) being lower than the melting point of the at least one first metal material, and the first end (1) and the end plug (11) are fixed relative to each other by friction brazing.

2. The fuel rail (100) according to claim 1, wherein: A second metal material (20) is arranged between the first end (1) and the end plug (11) around the central axis (A), the melting point of the second metal material (20) being lower than the melting point of the at least one first metal material, and the first end (1) and the end plug (11) are fixed relative to each other by friction brazing.

3. The fuel rail (100) according to claim 1 or 2, wherein: The first metal material is stainless steel.

4. The fuel rail (100) according to any one of claims 1 to 3, wherein: The first end (1) and the end plug (11) are fixed relative to each other by friction brazing, and the second metal material (20) includes copper.

5. The fuel rail (100) according to any one of claims 1 to 4, wherein: The fuel rail includes an end connection (12) at a second end (2) remote from the first end (1), the end connection (12) being a fuel port.

6. The fuel rail (100) according to any one of claims 1 to 5, wherein: The fuel rail includes a plurality of side ports (13) distributed transversely between the first end (1) and the second end (2), the plurality of side ports (13) being in hydraulic communication with the tube hole (10).

7. The fuel rail (100) according to any one of claims 1 to 6, wherein: The fuel rail (100) is forged.

8. A method for producing a fuel rail (100), wherein: The method comprises the following steps: a) providing the fuel rail (100) with a cylindrical tube hole (10) extending along a central axis (A); providing a sealing plug housing provided with an end plug (11) for the first end (1) of the fuel rail (100); at least one first metal material forming the first end (1) and the end plug (11); b) aligning the end plug (11) with the first end (1) along the central axis (A) and pressing it onto the first end (1); c) rotating the end plug (11) relative to the first end (1) about a central axis (A) until the at least one first metallic material softens for friction welding; d) stopping the rotation of the end plug (11) relative to the first end (1); Alternatively, the method comprises the following steps: i. providing the fuel rail (100) with a cylindrical tube hole (10) extending along the central axis (A); providing a sealing plug housing provided with an end plug (11) for the first end (1) of the fuel rail (100); at least one first metal material forms the first end (1) and the end plug (11); ii. providing an annular sheet of a second metal material (20), the melting point of the second metal material (20) being lower than the melting point of the at least one first metal material of the first end (1) and the end plug (11); iii. aligning the end plug (11) along the central axis (A) with the first end (1) and pressing it onto the first end (1); iv. rotating the end plug (11) relative to the first end (1) about the central axis (A) until the second metal material softens for friction brazing; v. Stopping the rotation of the end plug (11) relative to the first end (1).

9. The method according to claim 8, wherein: The method comprises the following steps: i. providing the fuel rail (100) with a cylindrical tube hole (10) extending along the central axis (A); providing a sealing plug housing provided with an end plug (11) for the first end (1) of the fuel rail (100); at least one first metal material forms the first end (1) and the end plug (11); ii. providing an annular sheet of a second metal material (20), the melting point of the second metal material (20) being lower than the melting point of at least one first metal material of the first end (1) and the end plug (11); iii. aligning the end plug (11) along the central axis (A) with the first end (1) and pressing it onto the first end (1); iv. rotating the end plug (11) relative to the first end (1) about the central axis (A) until the second metal material softens for friction brazing; v. Stopping the rotation of the end plug (11) relative to the first end (1).

10. The method according to claim 8 or 9, wherein: The method comprises the following steps: before step (b) or step (ii), providing at least one annular gap (30) around the end plug (11) around the central axis (A).

11. The method according to any one of claims 8 to 10, wherein: The method comprises the following steps: setting the first metal material to stainless steel.

12. The method according to any one of claims 8 to 11, wherein: The method comprises the steps of fixing the first end (1) and the end plug (11) relative to each other by friction brazing, wherein the method further comprises arranging the second metal material (20) to comprise copper.

13. The method according to any one of claims 8 to 12, wherein: The method comprises the following steps: providing an end connection portion (12) at a second end (2) of the fuel rail (100) away from the first end (1), the end connection portion (12) serving as a fuel port.

14. The method according to any one of claims 8 to 13, wherein: The method comprises the following steps: providing the fuel rail (100) with a plurality of side ports (13) distributed transversely between the first end (1) and the second end (2), wherein the plurality of side ports (13) are hydraulically connected to the tube hole (10).

15. Use of friction welding or friction brazing for securing an end plug (11) to a first end (1) of a fuel rail (100).

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