WO2004069446A1

WO2004069446A1 - Method for the production of a high-pressure fuel tank

Info

Publication number: WO2004069446A1
Application number: PCT/DE2003/003084
Authority: WO
Inventors: Markus Degn; Thomas Rahn
Original assignee: Robert Bosch Gmbh
Priority date: 2003-02-06
Filing date: 2003-09-17
Publication date: 2004-08-19
Also published as: DE10304961B3

Abstract

The invention relates to a method for producing a high-pressure fuel tank for a common rail fuel injection system used for internal combustion engines. According to said method, the high-pressure fuel tank is formed by kneading in a rotary manner a blank (1) comprising a longitudinal hollow space (3) with the aid of rotary kneading tools (5) and is then completed by means of additional processing steps.

Description

Process for the production of a high pressure raft

Technical field

An injection system is used to supply an internal combustion engine with fuel. In the accumulator injection system called common rail system, pressure generation and injection are decoupled from one another in time and place. A separate high-pressure pump generates the injection pressure in a central high-pressure fuel reservoir. The start of injection and the injection quantity are determined by the actuation time and duration of electrically actuated injectors which are connected to the high-pressure fuel reservoir by fuel lines. During operation, extremely high pressures occur in the K-raft high-pressure accumulator, which is why very high demands are placed on its pressure resistance.

State of the art

In the prior art, the high-pressure fuel accumulators are forged, drawn or rolled.

DE-A 199 36 533 relates to a high-pressure fuel accumulator for a common rail fuel injection system of an internal combustion engine with a tubular base body which has a blind bore running in the longitudinal direction and a plurality of connections.

From DE-A 199 49 962 a further high-pressure fuel reservoir for a common rail fuel injection system of an internal combustion engine is known. The high-pressure fuel accumulator has a hollow base body which is equipped with a plurality of connection openings. The interior of the base body is flat in the area of the connection openings. DE-A 199 45 316 also relates to a high-pressure fuel accumulator for a common-rail fuel injection system of an internal combustion engine with a tubular base body, the interior of which is connected to a plurality of connection openings. In order to increase the high-pressure strength, the interior is arranged eccentrically with respect to the longitudinal axis of the base body.

The high-pressure strength of the high-pressure fuel reservoir is mainly limited by the intersections between the connection openings and the interior of the base body. These drilling intersections are heavily loaded by the internal pressure and represent possible failure points of the high-pressure fuel pressure accumulator. During operation, stress peaks occur there, which can cause cracks in the base body.

Presentation of the invention

An advantage of the present invention is that high-pressure fuel accumulators can be produced which have an increased pressure resistance. The method according to the invention enables the construction of the fuel pressure accumulator to be adapted to an optimum in terms of its pressure resistance. Above all, inner shapes can be produced, but also outer shapes that are ideally adapted to the stresses that occur during operation. Further advantages of the present invention are better material utilization and less expensive production than in the prior art.

These advantages are achieved according to the invention by a method for producing a high-pressure fuel accumulator for a common-rail fuel injection system for Bre nkraftmaschinen, the high-pressure fuel accumulator being formed by circular kneading with circular kneading tools of a blank containing a longitudinal cavity and then completed by further processing steps.

Round kneading (round hammering) is a non-cutting manufacturing process for reducing the cross-section of bars, tubes and wires. The force is applied directly to the circumference of the workpiece by multiple tools. Circular kneading is an incremental forming process, which means that the forming work is not carried out in one tool stroke, but that the workpiece is processed in many small individual steps. During circular kneading, the tools completely or partially enclose the cross-section to be reduced, at the same time act radially and / or move relative to the workpiece about the pass axis. Almost any metallic material can be kneaded with a circular kneading process processed, provided there is sufficient elasticity of the material. Sintered materials can also be kneaded round. Workpieces, for example made of tungsten and nickel alloys, can also be machined on rotary riveting machines, and in exceptional cases the material of the machine can also be fed in when heated. In the case of solid bars, the reduction in the outer diameter leads to an extension of the workpiece at the ends. Pipes are subject to a complicated flow of materials. Increase in length,

The decrease in inner diameter and the increase in wall thickness change and influence each other depending on the material properties and the tool geometry. Basically, the total volume remains constant when incompressible materials are processed.

Circular kneading advantageously increases the tensile strength, depending on the decrease in cross-section and the hardening behavior of the material. Furthermore, with an increasing reduction in cross-section, the surface of the blank formed by kneading is significantly improved. Compared to machined surfaces, the surface of the kneaded workpiece has a much lower surface roughness.

Circular kneading as part of the manufacturing process for high-pressure fuel accumulators (rails) therefore allows

1. a stress-oriented shape of the rail,

2. the generation of residual compressive stresses in the rail, which counteract the high pressure load,

3. achieving an increase in strength of the rail and

4. the achievement of a high surface area -g ₀ ute.

All of these advantages of rotary kneading contribute to the high pressure resistance of a high-pressure fuel reservoir produced by the method according to the invention.

Circular kneading machines are generally known in the prior art, for example from DE-A 199 55 323 and DE-A 199 55 321. Various circular kneading machines from the prior art allow a with a comparatively simple machine concept Circular kneading with tools that impact radially on a tool and rotate relative to the workpiece.

The blank containing a longitudinal cavity from which the high-pressure fuel accumulator is produced in the present invention preferably corresponds to the blanks from which welded high-pressure fuel accumulators are usually manufactured in the prior art. These blanks therefore consist of a material suitable for welding and forming, for example 20MnCrS5, which is tempered and peeled. Such a blank also contains a longitudinal cavity which has preferably been drilled cylindrically deep-hole. Alternatively, after the deep hole boring work step, surface smoothing manufacturing steps such as. B. Lapping or mounds can be connected. This advantageously enables a further improvement in the surface quality after the round kneading to be achieved.

The present invention furthermore relates to a high-pressure fuel reservoir for a common-rail fuel injection system, produced by the method according to the invention, the high-pressure fuel reservoir being able to be manufactured, for example, from a material such as 20 MnCrS5. In general, a high-pressure fuel accumulator configured according to the invention can be produced from cold or semi-hot formable materials which have a suitable strength range (Rm ~ 800-1300 N / mm ² ). To further assembly steps such. B. to allow the connection to the high-pressure accumulator, the cold or semi-hot formable material should also be suitable for welding or soldering.

drawing

The invention is explained in more detail below with the aid of the drawing.

FIG. 1 shows a blank from which a high-pressure fuel accumulator is produced by the method according to the invention,

FIG. 2 round kneading of a blank using a dome,

FIG. 3 shows an embodiment of a blank machined by kneading, 4 shows a further embodiment of a blank machined by kneading and

FIG. 5 shows an embodiment of a high-pressure fuel reservoir according to the invention produced by the method according to the invention.

Execution variants

FIG. 1 shows a blank from which a fuel high-pressure accumulator can be produced using the method according to the invention.

The blank 1 comprises a base body 2 with a longitudinal cavity 3. The longitudinal cavity has a cylindrical shape and is arranged in the center of the blank 1. Due to the central arrangement of the longitudinal cavity 3, the longitudinal axis 4 represents both the axis of symmetry of the longitudinal cavity 3 and of the entire cylindrical blank 1.

A section through the blank 1 perpendicular to the longitudinal axis 4 is shown on the right-hand side of FIG. Sowolil the blank 1, as well as the contained therein

Longitudinal cavity 3 have a circular cross section. The longitudinal cavity 3 with the cavity diameter D _H lies centrally in the base body 2 of the blank 1 with the

Outside diameter D _A - it is also conceivable (in relation to the longitudinal axis 4) for the longitudinal cavity 3 to be arranged eccentrically in the base body 2. This results in a changing wall thickness d of the base body surrounding the longitudinal cavity 3

2. Necessary intersections of transverse cavities with the interior of the base body 2, which are required in the finished high-pressure fuel reservoir, can advantageously be arranged in the region of the greatest wall thickness d of the base body 2 surrounding the longitudinal cavity 3, so that the high-pressure strength of the high-pressure fuel reservoir is increased becomes.

The base body 2 is formed, for example, from a drawn starting material for producing the blank 1 shown in FIG. The longitudinal cavity 3 is preferably introduced into the base body 2 of the blank 1 by drilling.

Figure 2 shows the round kneading of a blank using a dome. The blank 1 is machined with tools 5 during kneading. Two tools 5 are shown in FIG. 2, which carry out an oscillating movement. Instead of the two segments shown, the method can also be operated, for example, with three, four, five or six tools 5, which are concentrically grouped around the blank 1. The arrows 6 indicate the movement of the tools towards the blank, through which the forming work is carried out.

In a preferred embodiment of the method according to the invention, the blank 1 is moved in the axial direction 9 relative to the round kneading tools 5 during the round kneading or the round kneading tools 5 are moved relative to the blank 1 in the opposite axial direction 9. In this method variant known as feed kneading, the blank 1 is moved step by step in the axial direction 9 by the oscillating tools 5. The feed movement takes place when the tools 5 are not touching the blank 1. Since the tools 5 oscillate at a high frequency, the feed movement is apparently continuous.

The surface of the respective tool 5 facing the workpiece during feed round kneading is beveled towards its edge. The bevel 10 of the tool surface in the direction of feed movement generates an enlarging chamfer on the outside 8 of the blank 1 when the tool 5 is oscillating. The bevel 11 of the tool surface on the side of the tool facing away from the feed movement direction serves to produce a surface that is as smooth as possible and prevents damage to the surface on the outside 8 of the blank due to the springback of the material.

As an alternative to feed round kneading, depending on the geometry to be displayed, the process variant of plunge round kneading can also be selected. This enables a local reduction in cross-section (also in the middle of the workpiece). This is done by a controlled opening and closing of the tools 5 superimposed on the actual tool stroke, this movement being substantially greater than the oscillation of the tools 5.

In a preferred embodiment of the method according to the invention, the blank 1 performs a rotary movement about its longitudinal axis 4 and / or during the kneading

Circular kneading tools 5 perform a rotational movement in the opposite direction of rotation around the blank 1. The rotational relative movement between tool 5 and blank 1 serves among other things, to prevent the material of the blank 1 from flowing between the tool segments.

In a preferred embodiment of the present invention, the outside 8 of the blank 1 is formed into a desired shape during the manufacture of the high-pressure fuel accumulator by the round kneading. The term "round kneading" only covers part of the process variations, since non-rotationally symmetrical profiles can also be produced. The shape of the outside 8 of the blank 1 depends on the geometry of the tools 5 and on the process variant used. For example, elliptical or polygonal shapes can be set for the outside 8, so that a stress-oriented design of the high-pressure fuel accumulator is possible. With regard to the placement of its high-pressure line connections, both in relation to the high-pressure lines leading to the fuel injectors and for the connection of the high-pressure delivery unit, the high-pressure fuel reservoir is generally designed in such a way that its geometry accommodates a simple line connection and also has strength advantages.

Outside surfaces that are as flat as possible are aimed for, as well as larger cross-bore lengths, so that your loads occur at the intersections of the cross-bore with the center bore of the high-pressure fuel accumulator. This can e.g. B. can be achieved by specifying an ovality.

In the production of the high-pressure fuel accumulator according to the invention, the inside of the blank 1 is preferably formed into a desired shape by the round kneading. When forming without a mandrel, the inner shape (the shape of the longitudinal cavity 3) is formed in the free flow. Since the forming is subject to the law of volume constancy, the material displaced by the reduction in the outside diameter must flow away. This happens on the one hand in the axial, on the other hand in the radial direction. If the outer diameter of the blank 1 is reduced, its wall thickness d increases and it becomes longer. If specific requirements are placed on the inner surface, such as dimensional accuracy, surface quality or if a specific inner profile is to be produced, a mandrel 7 must check the material flow inwards during the forming process.

In the preferred embodiment of the present invention shown in FIG. 2, a mandrel 7 protrudes at least into a section of the longitudinal cavity 3 of the blank 1 during the round kneading in order to produce a specific internal profile of the high-pressure fuel storage device. The mandrel 7 represents the negative of the Finished geometry of at least a portion of the longitudinal cavity 3 of the high-pressure fuel reservoir after the round kneading. The use of the dome 7 allows the production of a longitudinal cavity 3, the shape of which is subject to a close tolerance. The mandrel 7 can be cylindrical, conical or provided with a shoulder, for example. Furthermore, the production of more complex inner profiles is possible, such as different types of teeth, hexagon socket or swirl profiles. In addition to a cylindrical, a non-cylindrical or sectionally non-cylindrical internal geometry of the high-pressure fuel accumulator can also be generated.

In a preferred embodiment of the present invention, the dome 7 has an elliptical cross section. As a result, the longitudinal cavity 3 of the blank 1 is deformed during the round kneading by a combined axial and rotary feed of the blank 1 and the oscillating tool movement such that it also has an elliptical cross section. The mandrel 7 also moves during the combined axial or rotary feed.

FIG. 3 shows a preferred embodiment of a blank machined by kneading.

The longitudinal cavity 3 in the base body 2 of the blank 1 has an elliptical cross section 12, as can be seen from the section along the line AA on the right side of the figure. The outer diameter D _AI is smaller than the original outer diameter D _{A of} the blank 1 which has not yet been kneaded by round kneading. The blank 1 shown in FIG. 3 and shaped by means of round kneading has a cylindrical outer shape. Due to the suitable choice of tools 5 and the machining method, other external shapes can also be formed, for example an elliptical or polygonal outer cross section of the machined blank 1.

FIG. 4 shows a further preferred embodiment of a blank machined by round kneading.

In this preferred embodiment of the method according to the invention, the longitudinal cavity 3 in the base body 2 has a sectionally cylindrical and sectionally non-cylindrical shape 13. According to the invention, such a geometry is produced by kneading with dome 7. The section BB shown on the right side of FIG. 4 through the formed blank 1 is located in a section with a circular cross section of the longitudinal cavity 3. Section AA corresponds to the section shown in FIG. In this section, the Longitudinal cavity 3 has an elliptical cross section. In the transition region 14, the circular cross section 15 merges into the elliptical cross section 12 of the longitudinal cavity 3. The outer shape of the blank 1 is circular. The outer diameter D _A _> is smaller than the original outer diameter D _A and it can be equal to or different from the outer diameter D _{AI of} the blank shown in Figure 3.

FIG. 5 shows a preferred embodiment of a high-pressure fuel reservoir according to the invention produced by the method according to the invention.

In this case, a blank 1 with a longitudinal cavity 3 was first formed by circular kneading, so that a base body 2 with an elliptical cross section 16, which also contains a longitudinal cavity 3 with an elliptical cross section 12, was formed. The main axes of the two ellipses are perpendicular to each other. The rail was then completed through further processing steps. Connection pieces 17 were welded to the outside of the base body 2, the main axis of the elliptical cross section 12 of the longitudinal cavity 3 running perpendicular to the central axis 18 of the connection pieces 17 (section CC). In addition to being welded, the connecting pieces 17 can also be connected to the base body 2 by other suitable joining methods. To connect the interior 19 of the connecting piece 17 with the longitudinal cavity 3, transverse cavities 20 were introduced into the base body 2 by means of a machining process, for example drilling. The central axis of the transverse cavities 20 corresponds to the central axis 18 of the connecting piece 17. The intersections 21 are heavily loaded by the internal pressure during operation of the fuel pressure accumulator, since stress peaks occur there. The greater the ratio between the diameter of the longitudinal cavity 3 and the inside diameter of the respective transverse cavity 20, the higher the pressure resistance of the high-pressure fuel accumulator. Due to the elliptical shape 12 of the longitudinal cavity 3 in the preferred embodiment of the present invention shown in FIG. 5, the diameter of the longitudinal cavity 3 appears larger in the region of the intersection 21 than in the case of a round shape. As a result, the ratio between the diameter of the longitudinal cavity 3 and the inner diameter of the transverse cavity 20 is comparatively larger, so that a higher compressive strength of the fuel pressure reservoir is achieved. It is therefore advantageous if at least the section of the longitudinal cavity 3 into which the transverse cavity 20 of the connecting piece 17 opens has an elliptical cross section. Due to the elliptical cross section of the base body 2, the wall thickness d of the base body 2 surrounding the longitudinal cavity 3 is also greater in the area of the connecting piece 17 than in other areas (section CC). At both ends of the fuel pressure accumulator interfaces 22 for attachments or fasteners are also attached by machining.

LIST OF REFERENCE NUMBERS

Blank basic body, longitudinal cavity, longitudinal axis, tools, arrows, mandrel, outside of the blank, axial direction, cutting the tool surface in the feed movement direction, chamfering the tool surface on the side facing away from the feed movement direction, elliptical cross section of the longitudinal cavity, cylindrical and non-cylindrical internal geometry, in some cases, transition area, circular cross section of the longitudinal cavity, the connecting piece of the basic connecting piece of the base connector, elliptical cross-section of the basic connecting piece of the basic connecting piece of the central connecting piece of the basic connecting piece of the basic connecting piece of the central connecting piece of the basic connecting piece of the central connecting piece of the basic connecting piece of the central connecting piece of the basic connecting piece of the central connecting piece of the central connecting piece of the central connecting piece of the connecting piece of the central connecting piece of the central connecting piece of the central connecting piece of the connecting piece of the central connecting piece of the central connecting piece of the central connecting piece of the connecting piece of the central connecting piece of the basic connecting piece of the connecting piece of the central connecting piece of the basic connecting piece of the connecting piece of the basic connecting part of the basic connecting part of the basic connecting part of the connecting piece Interior of the connecting piece cross cavity intersections interfaces for attachments or closures

Claims

claims

1. A method for producing a high-pressure fuel accumulator for a common rail fuel injection system for internal combustion engines, characterized in that the high-pressure fuel accumulator is formed by circular kneading with circular kneading tools (5) of a blank (1) containing a longitudinal cavity (3) and is then completed by further processing steps.

2. The method according to claim 1, characterized in that in the manufacture of the high-pressure fuel reservoir, the inside and / or the outside of the blank (1) is deformed into a desired shape by kneading.

3. The method according spoke 1, characterized in that for the production of a certain internal profile of the fuel pressure accumulator a dome (7) during the round kneading protrudes at least into a section of the longitudinal cavity (3) of the blank (1).

4. The method according to claim 3, characterized in that the mandrel (7) has an elliptical cross section.

5. The method according to claim 3, characterized in that the mandrel (7) has a circular cross section.

6. The method according to claim 1, characterized in that the blank (1) during circular kneading in the axial direction (9) is moved relative to the circular kneading tools (5) and / or the circular kneading tools (5) relative to the blank (1) in the axial Direction (9) can be moved.

7. The method according to claim 1, characterized in that the blank (1) performs a rotary movement about its longitudinal axis (4) during kneading and / or

Rotary kneading tools (5) perform a rotary movement around the blank (1).

8. The method according to claim 1, characterized in that the further processing steps, the welding of connecting pieces (17), the drilling of transverse cavities (20) and the attachment of interfaces for attachment or

Include fastener parts (22) at the ends of the fuel pressure accumulator.

9. High-pressure fuel reservoir for a common rail fuel injection system, produced by the method according to one of claims 1 to 8, wherein the high-pressure fuel reservoir is made of 20 MnCrS5 suitable for welding and forming.

10. High-pressure fuel reservoir according to claim 9, characterized in that the high-pressure fuel reservoir has an at least partially elliptical longitudinal cavity (3).