DE102018110342B4 - Method of manufacturing a fuel rail - Google Patents

Abstract

A method for manufacturing a fuel distributor (1) which has a pressure accumulator pipe (2) for receiving pressurized fuel, the pressure accumulator pipe (2) having a forged base body (8) with a longitudinal cavity (11) and one end (13) of the pressure accumulator pipe (2), a closing piece (14) delimiting the longitudinal cavity (11) is joined, the closing piece (14) being inductively soldered into the end (13), characterized in that the pressure accumulator pipe (2) during the soldering process as well as in flushed with protective gas during the cooling phase.

Description

The invention relates to a method for producing a fuel distributor according to the features in the preamble of claim 1.

A fuel rail is part of a fuel supply or a fuel injection system and is used to supply fuel to injectors of an internal combustion engine. In this case, statically compressed fuel is stored in a pressure accumulator pipe and distributed to the injectors or injection valves of a cylinder bank.

From the WO 2016/187314 A1 a fuel distributor is known with a pressure accumulator pipe, the ends of which are closed by soldered-in end caps.

the DE 295 21 402 U1 discloses a fuel rail in which the accumulator tube is formed by forging. The pressure accumulator pipe is closed on its one end and is designed as an axially directed connecting piece on its other end.

The prior art also includes a high-pressure fuel accumulator according to WO 01/09507 A1 . In order to improve the high-pressure resistance and to extend the service life of the high-pressure fuel accumulator, a sealing plug is arranged in the closed end of the blind hole.

Furthermore, the DE 20 2015 105 989 U1 a fuel rail having an accumulator tube for receiving pressurized fuel.

From the DE 25 55 960 B1 is also a method for soldering a hollow cylindrical body or the like. With a press fit at least partially arranged in this body.

Further state of the art is through the JP 2018-021539 A and the DE 10 2012 001 926 A1 educated.

In the case of fuel distributors with forged pressure accumulator pipes, the main body of the pressure accumulator pipe is usually machined by drilling and turning or milling. As part of the mechanical processing, a central bore is drilled lengthwise into the forging blank. This longitudinal cavity forms the pressure accumulator area. In addition, all other functional areas, such as B. Injector recordings, sensor interfaces and fuel supply are machined.

As a rule, the longitudinal cavity is closed by a screw plug or a screw cap. To do this, a thread and a sealing seat must be milled into the blank. The sealing is metallic or with an additional sealing element. Complex processing of the component is necessary for such a screw-type closure of the pressure accumulator pipe. Furthermore, the screw plugs used are relatively expensive to manufacture and must be handled very carefully during the manufacturing and assembly process in order to avoid damage to the sealing surfaces. If the metal seal fails, there is a risk that the leak through the seal in the thread will not be detected in the subsequent leak test. Furthermore, the assembly process as a whole is also necessary and is usually monitored for torque and angle of rotation. The end area of the pressure accumulator pipe, in which the screw plug is arranged, must also be made thicker in order to provide sufficient wall thickness for the thread.

As stated above, fuel rails are also known which are closed at one or both ends by means of closing pieces such as plugs which are soldered into the ends of the pressure accumulator pipe. For this purpose, the pressure accumulator pipe with the inserted closing pieces and applied solder is completely heated in a soldering furnace. However, this heating process normalizes the material of the accumulator tube, which reduces its strength and hardness.

Proceeding from the state of the art, the invention is based on the object of creating a method that is advantageous in terms of manufacturing technology for producing a fuel distributor with a pressure accumulator pipe that is improved in terms of pressure resistance.

According to the invention, this object is achieved in a method for producing a fuel distributor according to claim 1.

Advantageous refinements and developments of the method according to the invention for producing a fuel distributor are the subject matter of the dependent claims.

The fuel rail has an accumulator tube for receiving pressurized fuel. The main body of the accumulator tube is forged and has a longitudinal cavity. A closing piece delimiting the longitudinal cavity is fitted into one end of the pressure accumulator tube. According to the invention, the closing piece is inductively soldered into the end, with the pressure accumulator tube during the soldering process as well as in flushed with inert gas during the cooling phase, which prevents unwanted scaling and tarnishing.

The end of the pressure accumulator tube has a receiving section for the closing piece communicating with the longitudinal cavity. The locking piece is inserted into the receiving section and inductively soldered. Complex machining of the end, in particular the production of an internal thread and/or a sealing seat at the end, can be omitted.

The closing piece can be a deep-drawn, extruded or turned part.

When the closing piece is inductively soldered in, local inductive heating occurs in the area of the end of the pressure accumulator tube. As a result, the strain hardening achieved and desired by forging is retained in the component. This applies in particular to the highly stressed longitudinal cavity of the pressure accumulator tube.

The inductive heating for soldering the closing piece is limited to the joint area at the end of the pressure accumulator tube. The pressure accumulator pipe is not heated over its entire dimensions. As a result, a reduction in strength and hardness is avoided or reduced to a minimum. In addition, partial inductive heating is more energy-efficient and therefore cheaper than conventional furnace soldering.

To accommodate the closing piece, the end of the pressure accumulator tube has a receiving section for the closing piece. The receiving section is preferably cylindrical. In an advantageous embodiment, the receiving section merges into the longitudinal cavity via a step. The step can be designed to be very small, so that the diameter of the receiving section is only slightly larger than the diameter of the longitudinal cavity.

The closing piece can be a plug or a lid.

Furthermore, the closing piece can be a connecting piece. The connecting piece forms an interface for connecting components belonging to the injection system. For example, a fuel supply line or a pressure sensor can be connected to the connecting piece. For this purpose, the connecting piece has an outer coupling section. Preferably, the outer coupling portion is externally threaded. A fuel inlet or a pressure sensor can be connected by means of a union nut screwed onto the external thread.

For inductive soldering, the connection piece has an inner, in particular cylindrical, joining section. This is inserted and soldered into the end of the accumulator tube.

One aspect of the invention provides that the connection piece has a through channel, in particular a multi-stage through channel. In particular, a sealing seat or a sealing receptacle, for example in the form of a sealing cone, is formed in the connection piece.

To join the locking piece by soldering, a solid soldering ring is usually first mounted in the end. The closing piece is then inserted. During inductive heating, the solder material melts and, due to the capillary effect, is drawn into the assembly gap between the inner circumference in the receiving section of the end and the closing piece. If the process has been successful, this can be recognized by solder escaping at the front. This can easily be checked visually. A helium leak test is usually carried out downstream to rule out micro-leaks.

Inductive soldering eliminates the use of a soldering oven. In the brazing furnace, the material of the forged fuel rail or accumulator pipe would be normalized, reducing work hardening and hardness. However, this should be obtained according to the invention. The fuel distributor with the inductively soldered locking piece has only been inductively heated partially in the connection area. The strain hardening of the forged fuel distributor is thus retained. This significantly increases the pressure resistance of the pressure accumulator tube. The fuel distributor according to the invention reliably withstands the high pressures prevailing in the pressure accumulator pipe.

The inductive soldering of the fuel distributor or the pressure accumulator pipe with the closing piece is carried out in a soldering chamber. During the soldering process, the soldering chamber is filled with an inert gas, e.g. B. forming gas flushed. The generator of the inductive heating device can be designed as a high-frequency, low-frequency or medium-frequency generator. The induction coil is adapted to the component geometry so that the heating is limited to the end of the pressure accumulator pipe and the closing piece accommodated therein. The soldering temperature depends on the solder and is approx. 1100°C depending on the solder.

Due to the inductively soldered connection between the pressure accumulator pipe and the closing piece, a thickened end area of the pressure accumulator pipe for producing a connecting thread is omitted. At least the thickening can be designed to be smaller. The inside diameter of the receiving section is preferably equal to or slightly larger than the inside diameter of the longitudinal cavity.

The procedure according to the invention leads to a reduction in the processing effort, since no thread and/or sealing seat has to be milled on the pressure accumulator pipe. The invention enables an expensive locking screw to be replaced by a cheap locking piece. It is also advantageous that during assembly there is no need to monitor the torque and angle of rotation of the screwing operation of a locking screw.

• 1 einen erfindungsgemäß hergestellten Kraftstoffverteiler in einer perspektivischen Ansicht;
• 2 den erfindungsgemäß hergestellten Kraftstoffverteiler in einer Frontansicht;
• 3 einen Schnitt durch die Darstellung der 2 entlang der Linie A-A;
• 4 einen endseitigen Ausschnitt des Kraftstoffverteilers in einer Schnittdarstellung;
• 5 den endseitigen Ausschnitt einer weiteren Ausführungsform eines Kraftstoffverteilers und
• 6 den endseitigen Ausschnitt einer weiteren Ausführungsform eines Kraftstoffverteilers.

The invention is described in more detail below with reference to an exemplary embodiment illustrated in the drawings. Show it:

• 1 a fuel distributor produced according to the invention in a perspective view;
• 2 the fuel distributor produced according to the invention in a front view;
• 3 a cut through the representation of 2 along line AA;
• 4 an end detail of the fuel rail in a sectional view;
• 5 the end section of a further embodiment of a fuel distributor and
• 6 the end section of a further embodiment of a fuel distributor.

the 1 until 3 show a fuel distributor 1 according to the invention 4 a detail of the fuel distributor 1 is shown.

The fuel rail 1 is part of the accumulator injection system of an internal combustion engine. The generation of pressure and the fuel injection are decoupled from each other in such accumulator injection systems. A separate high-pressure pump continuously generates pressure. This pressure, which is built up independently of the injection sequence, is permanently available in fuel rail 1.

The fuel rail 1 includes a pressure accumulator pipe 2 with a pump-side high-pressure fuel connection 3 and a plurality of injector connections 4. The statically compressed fuel is stored in the pressure accumulator pipe 2 and distributed via the injector connections 4 to the injectors 5 of a cylinder bank. A pressure sensor 6 is connected to a pressure sensor port 7 .

The pressure accumulator pipe 2 has a forged base body 8 . To fix or assemble the fuel distributor 1 8 flange pieces 9 are provided on the base body. The flange pieces 9 are forged from the same material in one piece on the base body 8 and are provided with assembly openings 10 .

A longitudinal cavity 11 is introduced into the base body 8 by means of deep-hole drilling. The longitudinal cavity 11 is designed as a blind hole, so that one end 12 of the pressure accumulator tube 2 is closed. The other end 13 is closed by a closing piece 14 in the form of an end cap (see in particular 4 ). The closing piece 14 is inserted into the end 13 and soldered inductively. The closing piece 14 has a cylindrical socket section 15 with an interior space 16 that widens conically in the direction of the longitudinal cavity 11 and a cover wall 17 on the end face.

A receiving section 18 for the closing piece 14 is provided inside the end 13 . The receiving section 18 is matched to the axial length of the closing piece 14 so that the closing piece 14 terminates flush or almost flush with the end face 19 of the pressure accumulator pipe 2 . The receiving section 18 merges into the longitudinal cavity 11 via a step 20 . The receiving section 18 has a slightly larger inner diameter than the inner diameter of the longitudinal cavity 11.

For assembly, a solid soldering ring is inserted into the receiving section 18 and the closing piece 14 is inserted into the receiving section 18 . The components are then inductively soldered in a soldering chamber. In this case, only the area of the joint at the end 13 of the pressure accumulator tube 2 is partially heated inductively. During the soldering process, the soldering chamber is purged with an inert gas.

the 5 and 6 show embodiments of a fuel distributor 1 with different closing pieces 14.

At the fuel rail 1, from which in the 5 an end section is shown, the closing piece 14 is inductively soldered into the end 13 in the form of a solid cylindrical plug.

In the case of the 6 fuel rail 1 shown, a closing piece 14 is inductively soldered into the end 13, which is a connecting piece. The connection piece has an inner cylindrical joining section 21 and an outer coupling section 22 . With the joining section 21, the connection piece is inserted into the receiving section 18 in the end 13 of the pressure accumulator pipe 2 and comes to rest on the step 20 on the inside. The outwardly pointing outer coupling section 22 is provided with an external thread 23 . A further component, for example a fuel supply line or a pressure sensor, can be connected by screwing via the external thread 23 . A continuous, multi-stage through-channel 24 is provided in the connection piece. The passage channel 24 communicates with a sealing cone 25 which is introduced on the outer face of the coupling section 22 .

Reference List

1

fuel rail

2

accumulator tube

3

High pressure fuel connection

4

injector connection

5

injection injector

6

pressure sensor

7

pressure sensor connection

8th

body

9

flange piece

10

mounting hole

11

longitudinal cavity

12

end of 2

13

end of 2

14

locking piece

15

nozzle section

16

inner space

17

top panel

18

recording section

19

face

20

Step

21

joining section

22

coupling section

23

external thread

24

through channel

25

sealing cone

Claims (8)

A method for manufacturing a fuel distributor (1) which has a pressure accumulator pipe (2) for receiving pressurized fuel, the pressure accumulator pipe (2) having a forged base body (8) with a longitudinal cavity (11) and one end (13) of the pressure accumulator pipe (2) a closing piece (14) delimiting the longitudinal cavity (11) is joined, the closing piece (14) being inductively soldered into the end (13), characterized in that the pressure accumulator pipe (2) during the soldering process as well as in flushed with protective gas during the cooling phase. Fuel rail (1), produced by a method according to claim 1 , characterized in that the end (13) has a receiving portion (18) for the closing piece (14). Fuel distributor (1) after claim 2 , characterized in that the receiving section (18) merges into the longitudinal cavity (11) via a step (20). Fuel distributor (1) after claim 2 or 3 , characterized in that the closing piece (14) is a plug or end cap. Fuel distributor (1) after claim 2 or 3 , characterized in that the closing piece (14) is a connecting piece. Fuel distributor (1) after claim 5 , characterized in that the connecting piece has an inner joining section (21) and an outer coupling section (22). Fuel distributor (1) after claim 6 , characterized in that the coupling section (22) has an external thread (23). Fuel distributor (1) according to one of Claims 5 until 7 , characterized in that the connection piece has a through channel (24).

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