Fuel rail and method of making a fuel rail

Abstract

A forged fuel rail for a motor vehicle includes a tubular base body, an inlet formed in one piece on the base body and made of a same material as the base body. Further formed in one piece on the base body and made of a same material as the base body are a plurality of injector mounts and, a support element for securement of the fuel rail to a further motor vehicle component. A reinforcement member extends between a corresponding one of the injector mounts and the support element and is formed in one piece on the base body and made of a same material as the base body. The reinforcement member is hereby formed from a flash created during a forging process.

Claims

1. A forged fuel rail, comprising: a tubular base body; an inlet formed in one piece on the base body and made of the same material as the base body; a plurality of injector mounts formed in one piece on the base body and made of a same material as the base body; a support element formed in one piece on the base body for securement to a further motor vehicle component; and a reinforcement member extending between a corresponding one of the injector mounts and the support element and formed in one piece on the base body and made of a same material as the base body, said reinforcement member having a free first edge shaped to be at a minimum extent in relation to an extent of the reinforcement member perpendicular to a longitudinal axis of the base body and distanced to the corresponding one of the injector mounts and the support element, wherein the reinforcement member has a second edge which is connected to the support element and defines with the free first edge of the reinforcement member a first angle, said reinforcement member having a third edge which is connected to the corresponding one of the injector mounts and defines with the free first edge of the reinforcement member a second angle, each of the first and second angles being less than 90.

2. The forged fuel rail of claim 1, wherein the corresponding one of the injector mounts and the support element extend in parallel relationship.

3. The forged fuel rail of claim 1, wherein the free first edge of the reinforcement member is shaped in the form of a continuous curve.

4. The forged fuel rail of claim 1, wherein the corresponding one of the injector mounts and the support element are adjacent to one another, with the reinforcement member extending there between.

5. The forged fuel rail of claim 1, wherein the free first edge is shaped to enable a shortest possible load path through the reinforcement member between an entry point of a force at the corresponding one of the injector mounts and an exit point of the force at the support element connected to the corresponding one of the injector mounts by the reinforcement member.

6. The forged fuel rail of claim 1, wherein the reinforcement member has a mean thickness of 2 to 6 millimeters.

7. The forged fuel rail of claim 1, wherein the reinforcement member has a variable thickness.

8. The forged fuel rail of claim 1, wherein the reinforcement member is formed from a flash formed during a forging process.

9. A method of making a fuel rail for a motor vehicle, comprising: shaping a blank in a forging tool through a forging process into a semi-finished product, thereby forming a flash; removing the semi-finished product from the forging tool; subjecting the semi-finished to a machining process; forming an injector mount and a support element on the semi-finished product such that the flash, when being cut, extends between the injector mount and the support element; and trimming the flash such as to shape a reinforcement member with a free first edge shaped to be at a minimum extent in relation to an extent of the reinforcement member perpendicular to a longitudinal axis of the semi-finished product and distanced to the injector mount and the support element, with a second edge which is connected to the support element and defines with the free first edge of the reinforcement member a first angle, and a third edge which is connected to the injector mount and defines with the free first edge of the reinforcement member a second angle, each of the first and second angles being less than 90.

10. The method of claim 9, wherein the forging tool is a split forging tool, with the flash being formed in a parting plane of the split forging tool.

11. The method of claim 9, wherein the forging process includes pre-forging and finishing forging.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:

(2) FIG. 1 is a perspective illustration of a fuel rail according to the present invention;

(3) FIG. 2 is a plan view of a semi-finished product before undergoing a machining process;

(4) FIG. 3 is a plan view of the fuel rail;

(5) FIG. 4 is an enlarged cutaway view of the fuel rail of FIG. 3;

(6) FIG. 5 is a sectional view of a base body in a region of an inlet;

(7) FIG. 6 is a sectional view of a base body in a region of a mount; and

(8) FIG. 7 is a side view of the fuel rail.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(9) Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments may be illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.

(10) Turning now to the drawing, and in particular to FIG. 1, there is shown a perspective illustration of a fuel rail according to the present invention, generally designated by reference numeral 1 and made through a forging process. The fuel rail 1 includes a tubular base body 2, an inlet 3 formed in one piece with a sidewall 7 of the base body 2 and made of same material, a plurality of injector mounts 4, formed in one piece with the base body 2 and made of same material, and support elements 5, formed in one piece with the base body 2 and made of same material. The fuel rail 1 is secured via the support elements 5 to a further motor vehicle component. Extending between adjacent injector mounts 4 and support elements 5 are reinforcement members 6, respectively, which are also formed in one piece with the base body 2 and made of same material as the base body 2. Provision is further made for a mount 8 for receiving a pressure sensor for determining an internal pressure.

(11) The support elements 5 are typically secured to the cylinder head (not shown) via a screw connection. For that purpose, the support elements 5 have screw holes 25 which are produced by a machining process. When installed, the support element 5 contacts the cylinder head with its contact plane 22, with bolts being placed perpendicular to the contact plane 22 through the screw holes 25 and into corresponding threads in the cylinder head. The contact plane 22 may also be suited to the surface of the cylinder head in order to attain a full surface-to-surface contact.

(12) When installed in a motor vehicle, the fuel injectors, which feed fuel into the cylinder head, are arranged in bores 12 of the injector mounts 4. During operation, fuel under pressure is injected via the injectors into the cylinder head. The resultant counterforce moves the injectors in a direction of the fuel rail 1. As a result of this movement of the injectors, a force is transmitted from the injector mounts 4 into the fuel rail 1. This causes a deflection of the injector mounts 4 out of their position at rest, while the support elements 5, which are firmly secured to the cylinder head, remain stationary. This causes deformation of the fuel rail 1 as a whole. The presence of the reinforcement members 6 counters this deformation to a minimum and ensures a lasting, error-free and fuel-tight operation of the fuel rail 1 by keeping any deflection of the injector mounts 4 to an admissible value below 1/10 of a millimeter. The reinforcement members 6 thus provide an effective stiffening of the fuel rail 1.

(13) As shown in FIG. 1, the reinforcement members 6 respectively extend between an injector mount 4 and an adjacent support element 5. Of course, it is within the scope of the present invention, to provide a reinforcement member 6 also between adjacent injector mounts 4 to provide added stiffening, if need be.

(14) The fuel rail 1 according to the present invention is produced by initially placing a blank in a forging tool. Depending on the complexity of the finished structure, the blank is shaped in one or more manufacturing steps into a semi-finished product 13, as shown by way of a plan view in FIG. 2. Inlet 3, mount 8, injector mounts 4, and support elements 5 are hereby formed in one piece with and of same material as the base body 2. While the blank is forged into the semi-finished 13, a flash 14 is formed in one piece and of same material.

(15) When being removed from the forging tool, the semi-finished product 13 undergoes a machining process, e.g., to produce a blind bore that results in an interior space 23 (FIGS. 5, 6) of the base body 2. A first end face 9 of the base body 2 remains hereby intact, whereas the opposite second end face 11 is pierced and closed by a plug 10, after the interior space 23 has been created. Also the bores 12 for the injector mounts 4, the inlet 3, the mount 8 for a pressure sensor, and the screw holes 25 are produced. It is to be understood that the term machining process includes any material removal process as well as cutting, beveling, or trimming.

(16) As is readily apparent from the sectional views of FIGS. 5 and 6, the interior space 23 has a round cross section. This is beneficial in terms of the resistance force against the internal pressure. The cross section remains also constant over the entire length of the base body 2. Of course, a different machining process may be applied in order to shape the semi-finished product 12 with other cross sections. For example, wall thicknesses are conceivable in at least some areas to suit stress, caused by the internal pressure or external force impacts. In such situations, the cross section of the interior space 23 and thus the diameter of the round cross section may vary along the longitudinal axis 15 of the base body 2. Also conceivable is a non-round cross section.

(17) Locally adapted wall thicknesses may also be produced by varying the outer periphery perpendicular to the longitudinal axis 15 of the base body 2 over its length. Then, the cross section of the interior space remains constant.

(18) The flash 14 is trimmed to shape the reinforcement members 6. In a forging process with various tool parts, the flash 14 is formed, which to date has been considered waste, but its presence simplifies the forging process. An example involves drop forging with flash formation. The formation of the flash 14 simplifies the forging process and the forging tools since excess material can easily flow off so that there is no need for a particular sealing of the tool. As mentioned above, the produced flash 14 has been removed to date. This is ineffective and produces waste. This problem is now addressed by the configuration of the fuel rail 1 according to the present invention. The amount of waste of forging material is reduced, thereby saving costs. The forging tool is still simple to design, further reducing costs, and simplifies handling.

(19) In order to design the installation of the fuel rail 1 as simple as possible and also to reduce stress on the fuel rail 1 during operation, the injector mounts 4 and the support elements 5 are aligned in parallel relation. In other words, the longitudinal axes 16 of the injector mounts 4 and the longitudinal axes 17 of the support elements 5 extend perpendicular to the longitudinal axis 15 of the base body 2, as readily apparent from FIG. 3, and lie in one plane, here the drawing plane. This renders the screw-connection together with the installation of the injectors simple. The forging process is also simplified by this geometric configuration because the injector mounts 4 and the support elements 5 can be arranged in a parting plane of the forging tool.

(20) FIG. 4 shows an enlarged cutaway view of an end of the fuel rail 1 at the first end face 9. The reinforcement member 6 has edges 20a, 20b, 20c which are connected to the base body 2, injector mount 4, and support element 5. The reinforcement member 6 extends perpendicular from the longitudinal axis 15 of the base body 2 radially outwards. The free edge 19 of the reinforcement member 6 has a configuration in the form of an even steady curve. Reference signs E.sub.1, E.sub.2, E.sub.3 defined extents in perpendicular direction to indicate that the course of the free edge 19 is not constant and has a minimum 18 at the extent E.sub.2. The minimum 18 is spaced from the injector mount 4 and the support element 5. This means that the extents E.sub.1, E.sub.3 of the reinforcement member 6, as viewed perpendicular to the longitudinal axis 15 of the base body 2 in proximity to the injector mount 4 and the support element 5, respectively, are greater at all times than the extent E.sub.2 in the region of the minimum 18.

(21) This configuration has two objectives. Firstly, the load path between the force entry point at the injector mount 4 and the force exit point at the support element 5 is kept as short as possible to realize a stiffening effect. Secondly, the transitions between the injector mount 4 and the support element 5, on one hand, and the reinforcement member 6, on the other hand is kept as smooth as possible to eliminate any risk of cracks. In other words, there is no sudden transition of reinforcement member 6 to the injector mount 4 and the support element 5. Rather the reinforcement member 6 runs out gradually to the injector mount 4 and the support element 5, respectively, at an angle as defined between the free edge 19 of the reinforcement member 6 and the connected edge 20a adjacent to the support element 5, and at an angle as defined between the free edge 19 of the reinforcement member 6 and the connected edge 20c adjacent to the injector mount 4. Each of the angles and . is less than 90, advantageously less than 60. Currently preferred is an angle and of less than 45.

(22) The precise configuration of the reinforcement member 6 in terms of the angles and and also the radius of the curve, as described by the free edge 19, is dependent on the constructive situation at hand. As is apparent from FIG. 3 for example, the distances between injector mounts 4 and support elements 5 vary, so that the various reinforcement members 6 are not of identical configuration but rather differ in their configuration, since different load paths have to be taken into account. Still, any transition between the reinforcement member 6 and the injector mount 4 or support element 5 is smooth.

(23) FIG. 5 shows a sectional view of the base body 2 of the fuel rail 1 in the region of the inlet 3. The orientation of the inlet 3 relative to the remaining construction of the fuel rail 1 is readily apparent. The longitudinal axis 21 of the inlet 3 and the contact plane 22 of the support element 5 define an angle . The contact plane 22 is to be understood as the plane along which the support elements 5 contact a further structure, such as the cylinder head. The angle is 60 to 80, advantageously 65 to 75. Currently preferred is an angle of 70 to 73.

(24) FIG. 6 shows a sectional view of the base body 2 in a region of the mount 8. The longitudinal axis 24 of the mount 8 and the contact plane 22 of the support element 5 define an angle . The angle is 70 to 90, advantageously 75 to 85. Currently preferred is an angle of 79 to 81.

(25) The fuel rail 1 is secured via the support elements 5 to the cylinder head, for example by a screw connection via the screw holes 25. Corresponding bolts are guided perpendicular to the contact plane 22 through the screw holes 25. The described arrangement of inlet 3 and mount 8 enables access to the screw holes 25 from above, thereby simplifying assembly of the fuel rail 1. At the same time, the inlet 3 for fuel supply and the mount 8 for signal lines of the pressure sensor are still easily accessible in the installation position.

(26) FIG. 7 shows a side view of the fuel rail 1, viewed in the direction of the injector mounts 4. As is readily apparent, the reinforcement members 6 have in the non-limiting example, shown in FIG. 7, a uniform thickness d which amounts to 2 to 6 millimeters, advantageously 2.5 to 4.5 millimeters. Currently preferred is a thickness d of 4 millimeters. Also readily apparent is the extent of the reinforcement members 6 perpendicular from the longitudinal axis 15 of the base body 2 radially outwards.

(27) Of course, there is no need for the thickness d to be constant over the entire extent of the reinforcement members 6. The thickness d may vary in the direction of the longitudinal axis 15 of the base body 2 and perpendicular to the longitudinal axis 15. This may further optimize the stiffening effect. Still, the thickness d should amount across the total area of the reinforcement member 6 on average 2 to 6 millimeters, advantageously 2.5 to 4.5 millimeters, or as currently preferred 4 millimeters.

(28) While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.