EP2809941B1 - Fuel distributor bar - Google Patents

Description

The invention relates to a tubular fuel rail, the end is closed with a plug which is inserted into the fuel rail and soldered to it.

The distribution of fuel to individual cylinders of an internal combustion engine is usually carried out by a tubular fuel rail, which is arranged in the vicinity of a cylinder head and is secured by means of retaining elements thereto. In the same distance as the cylinder openings are arranged on the fuel rail, in which injectors are used, which inject the fuel into the combustion chamber of the respective cylinder. At the end, the fuel rail is closed with plugs. Either the fuel feed is integrated into one of these plugs in the fuel rail or the fuel inlet takes place at another point of the fuel rail.

Usually, fuel is either gasoline or diesel. In the meantime, direct injection into the combustion chamber of the respective cylinder is carried out both in diesel engines and in modern gasoline engines. However, the operating pressures in the fuel rail differ considerably between diesel and gasoline. The necessary pressure for diesel direct injection is relatively high. In a so-called common rail technology, it is about 1800 bar and rises up to 2500 bar in a so-called pump-nozzle technology. For gasoline, the usual working pressures are around 1 to 100 bar. Only with a high-pressure direct injection into a gasoline engine, the fuel rail must be designed for an operating pressure of 200 to 800 bar. This results in design differences in the fuel rail, depending on whether the fuel rail for a diesel engine, a gasoline engine or a gasoline engine with modern direct injection is used at relatively high pressure.

The DE 10 2009 029 219 A1 shows a fuel rail for a diesel engine. It is a massive fuel rail, in which all connections for the injectors are integrally formed. At the end, plugs are screwed into the fuel rail via a thread. The wall thickness of the fuel rail is so strong that both a pipe wall of the fuel rail at the end inside is provided with a recess and the plug is in engagement with the recess and in the pipe wall with the return thread is introduced.

A similar structure of a fuel rail for diesel internal combustion engines shows the DE 101 62 203 A1 , In an integrally forged pipe, a pipe wall of the fuel rail is provided at the inside end with a recess and a thread into which a plug is screwed.

Such strong wall thicknesses are not available for fuel distribution strips for gasoline, since here the entire fuel rail is due to the significantly lower operating pressures of a relatively thin-walled tube. At an injection pressure of less than 10 bar, a generic fuel rail, for example, from a stainless steel pipe with a wall thickness manufactured under 1 mm. Typically, end plugs are soldered to the fuel rail. This design is excluded in a fuel rail for a high pressure diesel application, as it does not withstand the operating pressure of more than 1800 bar.

The DE 100 42 540 C1 shows a thin-walled fuel rail, which consists of an inner tube and a surrounding reinforcement. The end of the inner tube is closed on one side with a stopper, on the other side a plug is arranged, in which a connecting cable is inserted. The plugs are inserted into the inner tube and connected to this cohesively.

Likewise shows the DE 10 2008 044 923 A1 a fuel rail, the end is closed with a stopper. Both plugs are designed as cup-shaped thermoforming or sheet metal component, inserted into the fuel rail and soldered as well as other connection components with this.

As long as the operating pressure in fuel rail for gasoline engines in a range of a few bar, the just shown type is reliable. However, when demands are made on a fuel rail for gasoline to withstand an operating pressure of 200 to 800 bar safely, problems arise, but it would not make sense to dodge the usual in the diesel range forging solutions, because the operating pressure is not high enough. In particular, the joint between plug and fuel rail is loaded with different load cases. The load cases arise from a thrust force, which results from the internal pressure of the fuel on the inner surface of the plug, and from a tensile force in the joint, which is derived from the internal pressure in the tube to the inner surface of the tube. Consequently, the flow of force in the joint is deflected and thus causes increased stresses in the joint.

It is therefore an object of the present invention, a generic tubular fuel rail, which is closed at the end with a plug, which is inserted into the fuel rail and soldered to this, interpreted to an operating pressure of 200 to 800 bar.

This object is achieved by the invention with the features of claim 1. Accordingly, in a tubular fuel rail, which is closed at the end with a plug which is inserted into the fuel rail and soldered to this, a pipe wall of the fuel rail at the end inside provided with a return and the Plug is engaged with the return. This means that the pipe wall of the fuel rail is processed at the ends to be closed in such a way that continues after joining the pipe wall thickness of the fuel rail in the plug. For this purpose, the stopper on the side to be introduced into the fuel rail, a shoulder, so that an inner diameter of the plug at this point is equal to an inner diameter of the fuel rail without a jump. In this way, the approach of the plug is flush with the pipe wall of the fuel rail. As a result, the power flow is not distracted. In the fuel rail and the plug, a similar stress distribution is formed. In particular, there is no jump in stiffness and thus no notch effect in the joint. In this case, the plug in a particular embodiment on the outer peripheral side on a lying within the fuel rail groove for receiving a solder ring. The approach to the stopper prevents the solder from flowing into the interior of the fuel rail. The solder remains in the region of the groove and the immediately adjacent planar areas of the plug, so that it is ensured that enough solder is available for a cohesive connection of plug and fuel rail. In a further preferred embodiment variant, a passage for fuel is formed in the plug, with the passage preferably having at least two diameters of different sizes. For improved handling, the plug on the outer peripheral side has a mark lying outside the fuel rail. Plug and fuel rail are designed for an operating pressure of 200 to 800 bar and are usually used for gasoline fuel.

Figur 1

eine Draufsicht auf eine erfindungsgemäße Kraftstoffverteilerleiste (1),

Figur 2

einen Längsschnitt durch die erfindungsgemäße Kraftstoffverteilerleiste (1),

Figur 3

eine Detailansicht der Verbindung von Stopfen (5) aus Figur 2 mit der Kraftstoffverteilerleiste (1),

Figur 4

zeigt den Stopfen (5) aus Figur 3 vergrößert mit eingezeichnetem Längenverhältnis,

Figur 5

zeigt einen alternativen Stopfen (14) mit eingezeichnetem Längenverhältnis.

The invention is described in more detail below with reference to the figures. Showing:

FIG. 1

a top view of a fuel rail according to the invention (1),

FIG. 2

a longitudinal section through the fuel rail according to the invention (1),

FIG. 3

a detailed view of the connection of plug (5) FIG. 2 with the fuel rail (1),

FIG. 4

shows the plug (5) FIG. 3 enlarged with drawn aspect ratio,

FIG. 5

shows an alternative plug (14) with drawn aspect ratio.

In FIG. 1 the fuel distributor strip (1) according to the invention with a pipe wall (2), connection sockets (3) for injectors and holders (4) for fixing to an internal combustion engine in a plan view is shown. At the end, the fuel rail (1) with two different plugs (5) and (6) is closed.

FIG. 2 shows a longitudinal section through the fuel rail according to the invention (1). Through the plug (6), a supply of fuel through the passage (12) is possible. By way of a high-pressure pump (not shown), an operating pressure of 200 to 800 bar is set in the fuel rail (1). The passage (12) has different diameters, and that reduces the diameter in the direction of the fuel rail (1). This serves to throttle and calm the incoming fuel. In the plug (5) there is an opening (10) in which a non-illustrated pressure sensor is arranged, which monitors the pressure in the interior of the fuel rail (1). The fuel is supplied via the connection sockets (3) not shown cylinders of the internal combustion engine. Alternatively, both plugs may have a passage for fuel.

In FIG. 3 the plug (5) and the connection to the fuel rail (1) are shown in detail. The plug (5) has a stop (13). Up to this stop (13), the plug (5) is inserted into the fuel rail (1). The plug (5) has at its end a projection (7), which is located in the interior of the fuel rail (1). The fuel rail (1) is in her End region has been processed so that in the pipe wall (2) of the fuel rail (1) has a recess (11) has been introduced. In this recess (11) engages the projection (7) of the plug (5). The approach (7) closes flush with the pipe wall (2). In the region of the projection (7), the inner diameter of the plug (5) consequently coincides with the inner diameter of the fuel distributor strip (1) without a recess (11). The plug therefore continues the wall thickness of the fuel rail (1). This moves the joint from a relatively heavily loaded area. In the plug (5) is inside the fuel rail (1) on the outer peripheral side a circumferential groove (8) incorporated for a solder ring. By the approach (7) it is ensured that the solder remains in the region of the groove (8) and the adjoining joints and not uncontrollably migrates into the interior of the fuel rail (1) and so the joint is weakened. Return (11), shoulder (7) and circumferential groove (8) are also present at the plug (6). However, while in the passage (12) of the plug (6), the fuel in the fuel rail (1) is supplied, sits in the opening (10) of the plug (5), a pressure sensor. Consequently, the elements essential to the invention are realized in both plugs (5, 6) and at both ends of the fuel rail (1). However, since the plugs (5, 6) are not constructed completely identical, the plug (5) on the outer peripheral side has a marking (9) located outside the fuel distributor strip. The marking (9) serves a robot for distinguishing the two plugs (5) and (6), so that during assembly of the fuel rail (1) no confusion of the plug (5, 6) occurs. Alternatively, a fuel rail according to the invention may also be closed on both sides with identical plugs both with and without passage for fuel.

Ultimately, the stress distribution at the joint or in the joint seam is a decisive criterion for the durability of the fuel rail (1). Extensive strength tests have shown that a specific, in the FIGS. 4 and 5 exactly shown length ratio of an inner length L _{1 of} the approach (7) and an outer length L ₂ at the plug (5, 14) should not be exceeded. It shows FIG. 4 the stopper off FIG. 3 increased. On the one hand, the inner length L _{1 of} the attachment (7) is decisive. L ₁ is measured at the inside diameter of the plug (5), from a nose end (15) of the nosepiece (7) to a bottom (16) of the stopper (5). L ₂ is measured at the outer length of the plug (5). Plug (5) has a groove (8) which receives a solder ring, not shown. The groove (8) weakens the plug (5). In addition, forms for the joint connection a solder surface (17) of the groove (8) to the base end (15) of the projection (7), the supporting connection. The strength of the connection results from this solder surface (17). If the plug (5) is thus joined via a solder ring to the pipe wall (2) of the fuel rail (1), L _{2 is} measured from the groove (8) to the end of the neck (15). If one divides the thus determined outer length L _{2 of} the solder surface (17) on the plug (5) by the inner length L _{1 of} the projection (7), the ratio should be greater than or equal to 2, ie L ₂ : L ₁ ≥ 2.

Alternatively to the solder ring, the plug could also be pasted with a solder. In this case, a groove for receiving the solder ring is unnecessary. Such an embodiment is in FIG. 5 shown. In the stopper (14) shown here, a soldering surface (18) extends from the stop (13) to the attachment end (15). In this case, L _{2 is} also measured from the stop (13) to the extension end (15) of the plug (14). L ₁ is measured as well as the plug (5) from the approach end (15) to the bottom (16). Again, for an optimal stress ratio in the joint L ₂ : L ₁ ≥ 2 applies.

With D1 is in the FIGS. 3 to 5 the inner diameter of the fuel rail (1) without return (11) and the inner diameter of the plug (5, 6). The inner diameter D1 of the plug (5, 6) in the region of the projection (7) coincides with the inner diameter D1 of the fuel rail (1) without a recess (11). With D2, the outer diameter of the projection (7) or the inner diameter of the pipe wall (2) of the fuel rail (1) in the region of the recess (11) is designated. D3 indicates the outer diameter of the fuel rail (1).

LIST OF REFERENCE NUMBERS

1

Fuel rail

2

pipe wall

3

socket

4

holder

5

Plug

6

Plug

7

approach

8th

groove

9

mark

10

opening

11

return

12

passage

13

attack

14

Plug

15

approach the end

16

ground

17

solder surface

18

solder surface

L ₁

inner length

L ₂

outer length

Claims (8)

1. Tubular fuel distributor pipe (1) which is closed at the ends by a plug (5, 6), which is inserted in the fuel distributor pipe (1) and soldered thereto,
   characterised in that
   a pipe wall (2) of the fuel distributor pipe (1) is provided internally with a recess (11) at the end and the plug (5, 6) engages with the recess (11), wherein the said plug (5, 6) has a shoulder (7) on the side to be inserted in the fuel distributor pipe (1), so that an inner diameter of the plug (5, 6) at this point is equal to an inner diameter of the fuel distributor pipe (1) without a recess (11) and the shoulder (7) of the plug (5, 6) is flush with the pipe wall (2) of the fuel distributor pipe (1).
2. Tubular fuel distributor pipe (1) according to one of the preceding claims,
   characterised in that
   the plug (5, 6) has a groove (8) on the outer circumferential side of the fuel distributor pipe (1) to receive a solder ring.
3. Tubular fuel distributor pipe (1) according to any one of the preceding claims,
   characterised in that
   an outer length L₂ of the plug (5, 14) has a ratio of L₂ : L₁ ≥ 2 with respect to an inner length L₁ at the base of the plug (5).
4. Tubular fuel distributor pipe (1) according to one of the preceding claims,
   characterised in that
   a passage (12) for fuel is formed in the plug (6).
5. Tubular fuel distributor pipe (1) according to one of the preceding claims,
   characterised in that
   the passage (12) has at least two different-sized diameters.
6. Tubular fuel distributor pipe (1) according to one of the preceding claims,
   characterised in that
   the plug (5) has an indentation (9) on the outer circumferential side lying outside the fuel distributor pipe (1).
7. Tubular fuel distributor pipe (1) according to one of the preceding claims,
   characterised in that
   the plug (5, 6) and fuel distributor pipe (1) are designed for an operating pressure of 200 to 800 bar.
8. Tubular fuel distributor pipe (1) according to one of the preceding claims,
   characterised in that
   the fuel is petrol.

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