EP2789845A1 - Fuel distributor made from duplex steel - Google Patents

Abstract

The present application relates to a fuel distributor arrangement (1) for an internal combustion engine of a motor vehicle, comprising a fuel distributor strip (2) with a fuel distributor tube (3) and injector receptacles (4) branching off from the fuel distributor tube (3). The fuel rail (3) according to the invention is characterized in that it is formed of duplex steel.

Description

The present invention relates to a fuel rail arrangement according to the features in the preamble of claim 1.

From the prior art it is known to inject the fuel to an internal combustion engine. In this case, the injection process can take place in an intake pipe, in an antechamber or else alternatively directly into the combustion chamber. For this purpose, a fuel distributor is mounted on the internal combustion engine, wherein the fuel distributor is coupled to a fuel delivery pump. This fuel delivery pump generates in a fuel rail a pressure, operating pressure or nominal pressure (Pnenn) at high-pressure fuel injection lines of 300 bar to 400 bar, in particular 350 bar. The design is done: Pnenn * 1.5 = validation pressure.

It is known from the prior art that austenitic materials are used here in order to have a sufficient corrosion resistance in the ambient environment of an internal combustion engine as well as the delivery of fuels.

In the course of downsizing of internal combustion engines, which means an increase in output at a constant or reduced displacement, the fuel delivery pressures have increased. However, the requirements for the space or the packaging of the fuel rail itself have remained the same.

In order to ensure a sufficient reliability and also to ensure increased corrosion resistance to additives of the fuel, such as ethanol and methanol, an increase in the wall thickness must take place in the material used good. At the same time, however, this complicates the production of the fuel distributor, since, for example, the fuel distributor pipe or holder is produced by shaping machining, the forming itself being made considerably more difficult. By increasing the wall thickness, the volume of the pre-chamber must not be reduced. It is only an increase in wall thickness to the outside (in the space) possible.

Object of the present invention is therefore to show a fuel rail assembly that meets the current requirements for the expected operating conditions, taking into account the safety factor and at the same time is inexpensive to produce.

The aforementioned object is achieved with a fuel distributor assembly according to the features in claim 1.

Advantageous embodiments of the present invention are the subject of the dependent claims.

The fuel distributor arrangement according to the invention for an internal combustion engine of a motor vehicle has a fuel distributor rail with a fuel distributor pipe and branches off from the fuel distributor pipe Injektoraufnahmen and is inventively characterized in that the fuel rail and optionally the holder is formed of duplex steel.

According to the invention it is thus possible to realize a significantly higher strength at the same or reduced geometric dimensions. The austenitic proportions of the duplex steel itself also guarantee a sufficient resistance to occurring corrosion. Thus, it is possible to realize at least constant or reduced wall thicknesses compared to known from the prior art fuel rail, but at the same time withstand increased operating pressures and thus are designed to last longer.

In the context of the invention, it is possible to form at least the fuel rail of the fuel rail, thus the main distribution pipe of duplex steel. In the context of the invention, however, other attachments, for example, the branched off from the fuel rail injector or stopper plugs, mounting brackets or connection channels may also be formed of duplex steel. The individual components are in particular coupled to one another by means of a high-temperature soldering method at a temperature range between 500 ° C. and 1150 ° C. In particular, the following materials are used according to the invention: 1.4462, 1.4162, 1.4362 or 1.4662. The higher strength compared to the prior art is also given after brazing.

It is possible, with a wall thickness between 3 mm and 4 mm, in particular between 3.1 mm and 3.5 mm and particularly preferably of about 3.3 mm of the fuel rail operating pressures between 200 bar and 600 bar, in particular from 300 bar to 500 bar and most preferably of up to 500 bar with sufficient durability and durability. As a result of the at least constant, if not reduced, wall thickness compared with a comparable fuel distributor tube made of austenitic material, the weight of the fuel distributor arrangement according to the invention is reduced. If necessary, higher purchase costs of the duplex steel are compensated by lower processing costs during the forming and / or by a lower required volume. As a result, thus with constant and / or reduced geometric dimensions meet increased requirements for the operating configuration, with at least constant manufacturing costs and improved durability.

Another advantage is that other attachments, such as Injektoraufnahmen, Kraftstoffverteilerrohrbefestigungen and / or Kraftstoffverteilerrohrschellen and sealing plugs and / or passage plugs can be made of conventional austenitic steels and still be positively and / or cohesively coupled with the inventively duplex steel due to the material compatibility , Thus, for example, the production of the fuel rail made of duplex steel can be integrated into existing production facilities for known from the prior art fuel rail assemblies. This saves an investment overhead in the conversion of the plant to the inventive use of the duplex steel for the fuel rail.

Further preferably, the duplex steel has a nickel content, expressed in weight percent, between 0.1% and 5%, in particular between 0.1% and 3.5% and particularly preferably less than 3.5%. The low nickel content significantly reduces the risk of stress corrosion cracking. As a result, the durability of the fuel rail is increased at the same time.

Furthermore, the duplex steel preferably has the following alloying elements expressed in weight percent: chrome (Cr) 20 to 25% by weight molybdenum (Not a word) 2.50 to 3.50 wt.%,

Remaining iron and impurities caused by melting.

The structure of the duplex steel is preferably designed such that the proportion of ferrite corresponds to 50 to 70% and the proportion of austenite corresponds to 50 to 30%. The duplex steel further has, after brazing, a yield strength Rp0.2 of greater than or equal to 490 MPa and a tensile strength RM greater than or equal to 760 MPa.

This is achieved in the duplex steel grades used in particular by the fact that the joining process, thus the high-temperature soldering process according to the invention in less than ten minutes, more preferably in less than eight minutes, especially in less than six minutes and most preferably in less than five minutes. Thus, a heating up to more than 1,000 ° C Hochtemperaturlöttemperatur and a subsequent cooling to less than or equal to (≤) 400 ° C instead. The cooling itself follows in particular in a time window of less than four minutes. A sufficient strength of the prepared fuel rail assembly, in particular with regard to the solder joints is thus ensured without affecting the balance of the structural phases of austenite and ferrite of the duplex steel. In particular, the cooling process by gas cooling very particularly preferably by cooling with nitrogen instead of helium or argon instead to realize the requirements for the technical cleanliness of the component with simultaneous high cooling performance.

Figur 1

eine Kraftstoffverteileranordnung in perspektivischer Ansicht und

Figur 2

eine Kraftstoffverteileranordnung in Längsschnittansicht.

A preferred embodiment of a fuel rail according to the invention will be explained in the following description and shown schematically in the figures. These are for easy understanding of the invention. Show it:

FIG. 1

a fuel rail assembly in perspective view and

FIG. 2

a fuel rail assembly in longitudinal section view.

In the figures, the same reference numerals are used for the same or similar components, even if a repeated description is omitted for reasons of simplicity.

FIG. 1 shows a fuel distributor assembly 1 according to the invention in a perspective view. The fuel rail assembly 1 has a fuel rail 2, wherein the fuel rail 2 has a centrally extending fuel rail 3. From the fuel rail 3 are branched injector 4, wherein the injector 4, shown in FIG. 2 , coupled to the fuel rail 3 by means of thermal joint seam 5 are. According to the invention it is provided that the fuel rail 3 is formed of duplex steel, whereas, for example, the Injektoraufnahmen 4 may be formed of a conventional austenitic steel. Nevertheless, it is easily possible to couple the Injektoraufnahmen 4 with the fuel rail 3 via a thermal joint seam 5. Further, at the right-hand end of the fuel rail 3, which is related to the image plane, there is a closing plug 6 with a return line and on the left side a closing plug 7 with a supply line. By way of this it is again possible in each case to convey a fuel into an interior 9 of the fuel distributor tube 3, in which a validation pressure of up to 600 bar can be applied permanently. The fuel rail 3 itself has a wall thickness W, which is constant or reduced compared to conventional fuel rail 3, but at the same time higher resistance to increasing operating requirements. Further, mounting bracket 8 are at least positively coupled to the fuel rail 3, to couple it to an internal combustion engine, not shown, in particular on a cylinder head of an internal combustion engine.

Reference numerals:

1 -

Fuel rail assembly

2 -

Fuel rail

3 -

Fuel rail

4 -

injector socket

5 -

thermal joint seam

6 -

sealing plug

7 -

sealing plug

8th -

mounting bracket

9 -

inner space

W -

Wall thickness

Claims (7)

Fuel distributor arrangement (1) for an internal combustion engine of a motor vehicle, comprising a fuel distributor strip (2) with a fuel distributor pipe (3) and injector receptacles (4) branching off from the fuel distributor pipe (3), characterized in that the fuel distributor pipe (3) and optionally a holder (8 ) is formed of duplex steel. Fuel distributor arrangement according to claim 1, characterized in that the fuel distributor pipe (3) has a wall thickness (W) between 3 and 4 mm, in particular between 3.1 mm and 3.5 mm and preferably of 3.3 mm. Fuel distributor arrangement according to Claim 1 or 2, characterized in that the fuel distributor pipe (3) is designed for an operating pressure of between 200 and 600 bar, in particular of 300 to 500 bar, very particularly preferably of 500 bar. Fuel distributor arrangement according to one of Claims 1 to 3, characterized in that the fuel distributor strip (2) has further attachments, the attachments being coupled to the fuel distributor tube (3) by means of high-temperature soldering or brazing. Fuel distributor arrangement according to one of the preceding claims, characterized in that the low-loaded add-on parts are further formed from an austenitic steel. Fuel distributor arrangement according to one of claims 1 to 5, characterized in that the duplex steel has a nickel content expressed in weight percent between 0.1 and 5%, in particular between 0.1 and 3.5% and particularly preferably less than 3.5%. Fuel distributor arrangement according to one of claims 1 to 6, characterized in that all components are formed of duplex steel, wherein the components are preferably coupled together by means of a thermal joining method.

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