Fuel-rail assembly

Abstract

A fuel-rail assembly, comprising an injector having a proximally disposed inlet portion defining an inlet channel and extending along an axial direction, a fuel rail connected to the inlet portion via an outlet portion that defines an outlet channel, a nut element having an inner thread and at least indirectly engaging the outlet portion to transfer an axial clamp force by which a first contact surface of the inlet portion is pressed against a second contact surface of the outlet portion to provide a fluid-tight connection between the inlet channel and the outlet channel. In order to enable a wide flow path into an injector while maintaining an easy assembly process of the injector, the fuel-rail assembly comprises an adapter with an axially extending through-opening in which the inlet portion is at least partially received.

Claims

1. A fuel-rail assembly comprising: an injector having a proximally disposed inlet portion defining an inlet channel and extending along an axial direction, a fuel rail connected to the inlet portion via an outlet portion that defines an outlet channel, a nut element having an inner thread and at least indirectly engaging the outlet portion to transfer an axial clamp force by which a first contact surface of the inlet portion is pressed against a second contact surface of the outlet portion to provide a fluid-tight connection between the inlet channel and the outlet channel, an adapter with an axially extending through-opening in which the inlet portion is at least partially received, and with an outer thread that engages the inner thread, which adapter at least indirectly presses against the inlet portion to transfer the clamp force, wherein at least one intermediate element is interposed between the adapter and the inlet portion, and the adapter indirectly engages the inlet portion via the at least one intermediate element, wherein the intermediate element is a snap ring made of metal, wherein the inlet portion comprises a first annular recess which extends radially inwards and in which the snap ring is partially disposed, and wherein the adapter comprises a second annular recess which extends radially outwards and in which the snap ring is partially disposed.

2. The fuel-rail assembly according to claim 1, wherein the outlet portion is part of a high-pressure pipe, which is connected to the fuel rail.

3. The fuel-rail assembly according to claim 1, wherein at least one of the inlet portion and the adapter comprises a radially extending recess in which at least one intermediate element is partially disposed, and at least one intermediate element is elastically deformable to be movable into the recess.

4. The fuel-rail assembly according to claim 1, wherein the snap ring tangentially extends over between 400 and 340.

5. The fuel-rail assembly according to claim 1, wherein the first annular recess is at least partially defined by a first proximal surface that engages the snap ring and is inclined by less than 50 with respect to the axial direction, and a first distal surface, which is distally disposed from the first proximal surface and is inclined by more than 60 with respect to the axial direction.

6. The fuel-rail assembly according to claim 1, wherein the second annular recess is at least partially defined by a second proximal surface that is inclined by less than 50 with respect to the axial direction, and a second distal surface, which is distally disposed from the first proximal surface, which engages the snap ring and is inclined by more than 60 with respect to the axial direction.

7. The fuel-rail assembly according to claim 1, wherein the adapter comprises a thread portion, which comprises the outer thread and at least partially surrounds the mouth portion, and a second retainer portion, which engages the snap ring and which is disposed distally from the thread portion.

8. The fuel-rail assembly according to claim 1, wherein one of the first contact surface and the second contact surface is spherical and the other is conical.

9. The fuel-rail assembly according to claim 1, wherein the adapter comprises a distal entrance surface, which is distally disposed from the second annular recess and is inclined by less than 50 with respect to the axial direction.

10. The fuel-rail assembly according to claim 1, wherein the inlet portion comprises a mouth portion, which comprises the first contact surface, and a first retainer portion on which the first annular recess is disposed and which is disposed distally from the mouth portion.

11. The fuel-rail assembly according to claim 7, wherein a maximum radial outer dimension of the mouth portion is smaller than a maximum radial outer dimension of the first retainer portion, and a minimum radial inner dimension of the thread portion is smaller than a minimum radial inner dimension of the second retainer portion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

(2) FIG. 1 shows a first embodiment of an inventive fuel-rail assembly;

(3) FIG. 2 is a partial sectional view of a part of the fuel-rail assembly of FIG. 1; and

(4) FIG. 3A-3E illustrate different assembly stages of the fuel-rail assembly of FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS

(5) FIGS. 1 and 2 show a fuel-rail assembly 1 according to a first embodiment of the invention, which can be used in an internal combustion engine of e.g. an automotive vehicle. The fuel-rail assembly 1 comprises a fuel rail 10 that conveys and distributes fuel to a plurality of injectors 20, one of which is shown in the FIG. 1. Each injector 20 is connected to the fuel rail 10 by a high-pressure pipe 30. The fuel rail 10 and the high-pressure pipe 30 are made of metal. The pipe 30 has an outlet portion 31 that defines an outlet channel 32.

(6) The fuel rail 10 typically comprises an elongate tubular body being e.g. made from forged steel (e.g. stainless steel). The tubular body is generally hollow and defines an internal fuel reservoir or main channel that extends along the length of the tubular body. The main channel is connected to a high-pressure pump (not shown) that supplies fuel to the fuel rail at in a conventional manner. The fuel rail 10 further comprises a plurality of fuel injector interface portions, formed by radial projections, that are spaced apart along the length of the tubular body. In FIG. 1, nut 40 is connected to such outlet portion, and thus hidden.

(7) The injector 20 has an inlet portion 21 made of metal, which defines an inlet channel 22 that is parallel to an axial direction A, which also corresponds to a symmetry axis of the inlet channel 22. The inlet channel 22 is connected to the outlet channel 32 in the axial direction A, i.e., it communicates with the outlet channel 32 to receive fuel from the fuel rail 10 via the pipe 30. A first contact surface 25 of the inlet portion 21 is in contact with a second contact surface 33 of the outlet portion 31.

(8) The injector 20 conventionally comprises a nozzle valve with spray orifice(s) controlled by a needle that can be selectively reciprocally moved in order to open or close the nozzle. The needle is controlled by an actuator, generally comprising a solenoid.

(9) A nut element 40, in this case a cap nut, partially surrounds the outlet portion 31. An inward facing flange 41 of the nut element engages a collar of the outlet portion 31, thereby establishing an axial form fit. An inner thread 42 of the nut element 40 engages an outer thread 52 of a roughly annular adapter 50 that surrounds a major part of the inlet portion 21. In other words, a major part of the inlet portion 21 is received in an axially extending through-opening 51 of the adapter 50. The outer thread 52 is disposed in a thread portion 53 of the adapter 50 that surrounds a mouth portion 23 of the inlet portion 21. Distally from the mouth portion 23, a first retainer portion 24 of the inlet portion 21 is surrounded by a second retainer portion 54 of the adapter 50. A maximum outer radius R1 of the mouth portion 23 is almost identical to a minimum inner radius R2 of the thread portion 53, while a maximum outer radius R3 of the first retainer portion 24 is almost identical to a minimum inner radius R4 of the second retainer portion 54, so that there is only negligible radial play between the adapter 50 and the inlet portion 21. The maximum outer radius R1 of the mouth portion 23 (and the minimum inner radius R2 of the thread portion 53, respectively) is smaller than the maximum outer radius R3 of the first retainer portion 24 (and the minimum inner radius R4 of the second retainer portion 54). This allows for a comparably small outer thread 52 (in this case, an M14 thread), while on the other hand providing enough space for a first annular recess 26 that extends radially inward in the first retainer portion 24. On a proximal side, the first annular recess 26 is delimited by a first proximal surface 27, which in this case is inclined by about 40 with respect to the axial direction A. On a distal side, the first annular recess 26 is delimited by a first distal surface 28, which in this case is inclined by about 90 with respect to the axial direction A.

(10) The second retainer portion 54, and the other hand, comprises a second annular recess 55 that extends radially outwards. On a proximal side, the second annular recess 55 is delimited by a second proximal surface 56, which in this case is inclined by about 40 with respect to the axial direction A. On a distal side, the second annular recess 55 is delimited by a second distal surface 57, which in this case is inclined by about 70 with respect to the axial direction A. A snap ring 60, serving as an intermediate element, is partially disposed in the first annular recess 26 and the second annular recess 55. In this case, the snap ring 60, in its undeformed state, extends tangentially over 320, i.e. it has a 40 gap. Snap ring 60 thus acts a retainer ring and is generally formed as an annular member with a cut section (gap-circumference of less than 360) or having a bit more than one loop (when >360). The second distal surface 57 of the adapter 50 presses against the snap ring 60, which in turn presses against the first proximal surface 27 of the inlet portion. Accordingly, a flow of force runs from the outlet portion 31 through the nut element 40, the adapter 50 and the snap ring 60 to the inlet portion 21. This results in an axial clamp force pressing a conical first contact surface 25 of the inlet portion 21 against a spherical second contact surface 33 of the outlet portion 31. At its distal end, the adapter 50 comprises a distal entrance surface 58, which is in this case inclined by 40 with respect to the axial direction A. This distal entrance surface 58 has a special function during the assembly process of the fuel-rail assembly, which will now be explained with respect to FIG. 3A to 3E.

(11) During assembly, the snap ring 60 is fitted over the inlet portion 21. First, the snap ring 60 has to be radially expanded to be passed over the first retainer portion 24. As the position of the first annular recess 26 is reached, the snap ring 60 contracts and is partially received in the first annular recess 26, as shown in FIG. 3A. Afterwards, the adapter 50 is passed over the inlet portion 21 from a proximal end thereof, i.e., starting at the mouth portion 23. Since the minimum inner radius R4 of the second retainer portion 54 is considerably larger than the maximum outer radius R1 of the mouth portion 23, there is no or only minimal initial contact between the adapter 50 and the inlet portion 21. When the thread portion 53 reaches the mouth portion 23, as shown in FIG. 3B, the adapter 50 is axially guided since the minimum inner radius R2 of the thread portion 53 is almost identical to the maximum outer radius R1 of the mouth portion 23.

(12) When the distal entry surface 58 makes contact with the snap ring 60, this results in a radial force component that radially compresses the snap ring 60 and causes it to fully move into the first annular recess 26, as shown in FIG. 3C. Accordingly, the second retainer portion 54 can move further to the distal side without being hindered by the snap ring 60, which in turn is held back by the first distal surface 28. In a next phase, which is illustrated in FIG. 3D, the second annular recess 55 reaches the position of the snap ring 60, thereby allowing it to expand to its previous diameter. If the adapter 50 was moved distally from the position shown in FIG. 3D, the interaction of the second proximal surface 56 with the snap ring 60 would lead to a radial compression of the snap ring 60, resulting in axial force component that pushes the adapter 50 to the proximal side, thereby giving haptic feedback e.g. to an assembler.

(13) Next, the adapter 50 is pulled to the proximal side as the inner thread 42 and the outer thread 52 are screwed together. It should be noted that the adapter 50 as such is rotatable around the inlet portion 21, which may also facilitate the screwing process. As the adapter 50 moves proximally, the snap ring 60 is pulled along by its interaction with the second distal surface 57 so that it makes contact with the first proximal surface 27, as shown in FIG. 3E. The relatively moderate inclination of the first proximal surface 27 can lead to a gradually increasing force between the inlet portion 21, the snap ring 60 and the adapter 50.

LIST OF REFERENCE SIGNS

(14) 1 fuel-rail assembly 10 fuel rail 20 injector 21 inlet portion 22 inlet channel 23 mouth portion 24, 54 retainer portion 25, 33 contact surface 26, 55 annular recess 27, 56 proximal surface 28, 57 distal surface 30 pipe 31 outlet portion 32 outlet channel 40 nut element 41 flange 42 inner thread 50 adapter 51 through-opening 52 outer thread 53 thread portion 58 distal entrance surface 60 snap ring A axial direction R1, R3 maximum outer radius R2, R4 minimum inner radius