WO2005070579A2

WO2005070579A2 - High pressure storage line with a cast outer covering for a common-rail

Info

Publication number: WO2005070579A2
Application number: PCT/EP2005/050311
Authority: WO
Inventors: Matthias Stark
Original assignee: Schmitter Group Ag
Priority date: 2004-01-26
Filing date: 2005-01-25
Publication date: 2005-08-04
Also published as: EP1709320A2; WO2005070579A3

Abstract

The invention relates to a line for high-pressure fuel storage, oil or other liquids which are to be used in a common rail fuel injection system. Said line comprises an outer casting covering which is embodied in a tubular manner and which is made of casting material. One or several internal pipe parts are arranged inside the outer covering, and the outer covering is formed by recasting or extrusion coating one or several of the pipe parts.

Description

High pressure storage line with cast outer sheath for common rail

The invention relates to a line for the storage of high-pressure fuels, oil or other liquids, for use in a common rail fuel injection system, which consist of one or more inner tube parts and a tubular outer jacket, the outer jacket by casting around the inner tube parts is formed and to a method for producing such a line, according to independent claims 1 and 13.

Common rail fuel injection systems are injection systems for internal combustion engines in which an uncontrolled high-pressure pump brings the fuel to a high pressure level. The fuel pressurized in this way fills a pipeline system that is under constant pressure when the engine is operating. All cylinders of the engine are supplied with fuel from this common pipeline system, the injection being implemented by electronic control of the valves assigned to the respective cylinder. In contrast, in classic injection, each cylinder is connected directly to a piston of the pump, so that there is no connection between the individual cylinder fuel supply lines. The injection into the cylinders is controlled by the piston of the injection pump assigned to the cylinder, which builds up pressure in the line, through which the valve is opened and the fuel is injected.

The advantages of common rail technology lie in the extremely high injection pressures that can be achieved and in the possibility of realizing very short opening and injection times through the electrically controlled valves. This allows the injection process to be divided into different partial injections, for example one or more pre-injections, the main injection and one or more post-injections. Such a division of the injection process enables combustion overall are designed to be "softer" and thus a clean and more precisely controllable combustion can be realized. However, extremely high pressures are required to implement these injection systems, which therefore place very high demands on the pressure resistance of the pipeline used.

DE 101 40 058 A1 discloses a high-pressure fuel reservoir for a common rail fuel injection system, which is produced in one piece from a high-strength cast material. By manufacturing in the casting process, this high-pressure fuel accumulator can be produced in a favorable manner and with a variable design of the interior. However, it is disadvantageous that a high-strength casting material with sufficient wall thickness, which is relatively cost-intensive, has to be used to control the high pressures occurring and the extreme pressure fluctuations. Also, the spheroidal graphite cast iron used in accordance with DE 101 40 058 A1, like all cast iron, exhibits brittle deformation behavior, that is to say that no plastic deformation to a large extent is possible. Deformations beyond the elastic load capacity limit lead to cracks in brittle materials, which can lead to leaks or complete component failure.

The object of the invention is to provide a high-pressure fuel reservoir available, which shows a favorable behavior at high pressures and extreme pressure fluctuations and at the same time is easy and inexpensive to manufacture. This object is achieved by a high-pressure fuel accumulator according to claim 1. Further advantageous, optional embodiments and properties of the invention result from the dependent claims. A method for producing a high-pressure fuel accumulator according to the invention is specified in claim 17 and optionally in the following dependent claims.

A high-pressure fuel accumulator according to the invention for a common rail fuel injection system is realized by enclosing one or more inner tubes with an outer tube, the outer tube being cast or extrusion-coated around the inner tube by means of a castable or injectable material will be produced. This design of the high-pressure fuel reservoir surprisingly allows positive features of the different materials used for the individual components to be advantageously combined. For example, a material with high strength can be used as the inner tube, which is also particularly suitable for absorbing high pressures and strong pressure fluctuations due to its elastic and / or plastic deformation behavior. Steel or stainless steel pipes, for example, are suitable for this purpose, and their strength and rigidity can be improved by special processing steps such as forging and / or cold forming. However, since materials of this quality are very cost-intensive to procure and manufacture, in a high-pressure fuel accumulator according to the invention, part of the required strength can be obtained from the simple and inexpensive cast material with which the inner tube according to the invention is cast or extrusion-coated. On the other hand, the inner tube part (s) can be used to provide sufficient elastic longitudinal and transverse extensibility with the appropriate choice of material. The wall stability and thus the technical reliability are increased.

For the functioning of a high-pressure fuel accumulator in a common rail system, it is of great importance that the temperature of the fuel that is injected from the accumulator into the cylinder is not too high. Clean, low-pollution combustion is only guaranteed if the temperature of the fuel is sufficiently low. It is therefore desirable that a high-pressure fuel accumulator for use in a common rail fuel injection system is made of a material that can dissipate the heat generated by the compression of the fuel in the accumulator as well as possible. It is therefore advantageous to manufacture the high-pressure fuel accumulator according to the invention from materials with good thermal conductivity.

For the manufacture of the multi-part high-pressure fuel accumulator according to the invention, metallic materials, which are known to have good thermal conductivity, are therefore special Suitable dimensions. When the inner tube (s) of the high-pressure fuel accumulator is manufactured, for example, from steel and a cast iron is cast around the same tube, the close connection between the cast outer jacket and the inner tube part (s) that is produced during casting can optimally dissipate the heat generated without insulating cavities be guaranteed. By using steel as the material for the inner tube or tubes of the high-pressure fuel reservoir according to the invention, a high pressure resistance can also be achieved. Since local stress peaks can occur in the inner tube due to the geometry, the use of steel offers further advantages. In contrast to cast iron, steel has a ductile material behavior, ie plastic deformation behavior occurs when the load exceeds the elastic load limit. In this way, stresses can be "redirected" to less stressed areas, the component does not fail. A brittle material such as cast iron would break. For steel, therefore, lower safety surcharges are necessary for the design.

It has proven to be advantageous to design the ratio of the inner tube wall thickness to the wall thickness of the outer jacket in the range from 1: 5 to 1:15. The wall thickness ratio can vary in the course of the inner tube longitudinal axis in order to adjust the strength and the elastic or plastic properties to different requirements.

Such favorable properties of the inner tube can be further increased with the same diameter of the tube wall by using high-strength steels, for example stainless steels, without changing the dimensions of the high-pressure fuel reservoir. By varying the dimensions and / or wall ratios of the inner and outer tubes or the materials used, the high-pressure fuel reservoir according to the invention can be adapted to changing requirements with regard to pressure resistance without changing the geometry.

[0011] Alternatively, however, other materials for the High-pressure fuel accumulator according to the invention are used. In this way, high-strength components can also be produced from glass, since glass is very brittle, but has high strength and has the advantage of being very tight against liquids and gases. Very good strength properties can be achieved, particularly in the case of composite materials with glass. Materials with ceramics are another alternative. Since glass and ceramic materials also have good thermal conductivity, these materials can advantageously be used for a high-pressure fuel reservoir according to the invention.

As a further alternative, the use of plastics and plastic composite materials is also possible. In particular, since the maximum temperature of a common rail high-pressure fuel accumulator is limited by the permissible maximum temperature of the fuel during injection, the use of plastics is not faced with a fundamental problem in terms of material technology. Since the material parameters of a plastic can be set very well using modern plastics processing methods, an advantageous alternative in the field of materials technology for the high-pressure fuel reservoir according to the invention can be realized by using plastics. Thanks to their favorable strength / weight ratio, plastic materials are particularly suitable as a material for the cast outer jacket.

In an advantageous development of the high-pressure fuel accumulator according to the invention, the outer jacket of the accumulator is formed in several layers. Due to the production of the outer jacket in layers, suitable materials and / or material qualities can be used for different stress areas, as a result of which the high-pressure fuel accumulator according to the invention can be adapted even more precisely to the requirements and stresses. In this way, the profitability of the product can be further optimized. For example, in the case of a two-layer outer jacket made of gray cast iron, casting materials with different strengths can be used in the two layers. It would be conceivable, for. B. also the use of a fiber composite material for a layer to cover particular stress peaks.

A high-pressure fuel accumulator according to the invention can be used particularly advantageously in an arrangement as close as possible to the cylinders which are to be supplied with fuel by the injection system. It is therefore advantageous if outlets for the feed lines to the cylinder valves are already provided in the high-pressure fuel accumulator. For this purpose, the inner tube or tube structure is made from several individual tubes. The basis here is a longitudinal tube into which a certain number of cross tubes are inserted sideways. The number of cross tubes required is dependent on the number of cylinders that are to be supplied with fuel from the high-pressure fuel reservoir according to the invention. When producing the high-pressure fuel accumulator according to the invention with an inner tube made of a metallic material, in particular steel or stainless steel, these tubes can advantageously be connected to one another by soldering or welding. However, other methods for connecting the individual pipe parts are also conceivable, for example mechanical or mechanical thermal processing methods. It is conceivable, for example, that the pipe parts are connected to one another by pressure and heating (so-called diffusion welding process). Alternatively, a connection by reshaping pipe parts would also be conceivable.

In particular when using an inner tube made of a glass or ceramic material, it is advantageous to design the longitudinal tube with its cross tube outlets as a one-piece blank.

When operating the high-pressure fuel accumulator according to the invention in a common rail direct injection system, extremely high pressures occur in this accumulator. Common rail systems are operated with fuel pressures of up to 180 megapascals, further increases in fuel pressure are already planned to improve the combustion properties. This creates high voltages in the wall of the high-pressure fuel accumulator. The highest voltage peaks occur due to the design Intersections of the cross tubes with the inner tube. It is therefore advantageous to make the areas around the intersections of the cross tubes with the longitudinal tube particularly reinforced, for example by reinforcing the wall cross section of the inner tube parts in the course of the connection by welding by means of cladding. However, it is also conceivable to make the diameter of the outer jacket more pronounced in the area of the intersections. By adapting the overall cross section of the wall of the high-pressure fuel accumulator to the voltage actually occurring in the wall, the material requirement for the high-pressure fuel accumulator according to the invention can be optimized.

It is also advantageous to design the inner tube in the area of the cross tube connections with a smaller diameter, so that after casting at a constant overall diameter of the high-pressure fuel reservoir according to the invention, there is a significantly increased wall cross section at the connection points of the cross tubes with the longitudinal tube. Of course, it is alternatively possible to increase the diameter of the outer jacket at the junctures between the transverse and longitudinal tubes without a constant overall outer diameter.

The occurrence or the size of the stress peaks at the junctions between the transverse and longitudinal tubes is also dependent on the geometry of the corresponding tube section. The voltage peaks that occur become greater when the longitudinal tube is designed with a small radius at the junction with the cross tube. To reduce the stress peaks, it is therefore advantageous if the inner longitudinal tube is elliptically shaped, at least in the area of the connection points between the transverse and longitudinal tubes, in such a way that the longitudinal axis of the associated transverse tube is located in the extension of the shorter axis of symmetry of the elliptical shape. This gives the connection point a significantly lower curvature, which reduces the voltage peaks that occur. Depending on the application, other cross-sectional shapes can also be advantageous. It is conceivable to design the cross-sectional shape of the interior as a polygon, or even one Free form to choose.

For the production of a high-pressure fuel accumulator according to the invention, a casting mold is expediently used, into which a prepared blank for the inner pipe or pipes can be placed and can be cast or overmolded with a molten or liquefied casting material. It is possible that metallic or non-metallic materials can be used both for the cast outer jacket and for the prefabricated inner blank. Steels, glass or ceramic materials or composite materials are particularly suitable for the inner blank. The outer jacket can advantageously be produced, for example, with cast iron, in particular spheroidal graphite cast iron GGG40, or from a glass, ceramic or plastic material. Mixed forms are also possible, for example the use of a metal for the inner tube parts and a non-metal for the outer jacket or vice versa. The use of composite materials made of metals and non-metals is also possible.

In the manufacture of an inventive

High-pressure fuel accumulator with a multilayer outer jacket, it is advisable to use several molds for production. The inner tube blank is placed in the first mold, overmolded or cast with the material provided for the first layer and then removed from the mold for cooling and / or curing. When the level of maturity of the layer required for further processing has been reached, the resulting blank is placed in the next mold and then cast or overmolded again. This process is repeated until the desired number of layers is reached.

It is expedient to first prefabricate the inner tube parts or the blank of the inner tube separately to produce a high-pressure fuel reservoir according to the invention. Here, the prefabrication of the longitudinal tube is particularly important in order to achieve the adapted inner tube cross-sectional areas. When using steel or another plastically deformable material for the inner tube, this processing can advantageously be carried out by means of mechanical or mechanical-thermal forming processes. For example, an elliptical cross-section can be achieved when using an inner tube blank with a circular cross-section as follows: A mandrel with an elliptical cross-section is then inserted into the inner tube, which corresponds to the desired inner cross-sectional area of the high-pressure accumulator. The inner tube can then be pressed cold or warm around this mandrel, depending on the desired strength properties. A mandrel adapted to the desired cross-sectional shape can be used for the production of other cross-sectional shapes.

The same procedure is followed in the production of a longitudinal tube with a variable cross-sectional area. In the areas in which the cross-section is to be changed, a mandrel is inserted which corresponds in its cross-sectional area to the desired inner cross-sectional area of the area to be changed. Then this area is brought to the new shape using mechanical or mechanical - thermal forming techniques such as pressing, hot or cold drawing. The mandrel is then removed from the inside of the tube.

Following the production of such an inner longitudinal tube blank, this is connected to the cross tubes to form an inner tube blank. This inner tube blank is then introduced into the casting mold and cast or extrusion-coated there with the intended casting material.

In the application of the invention

High-pressure fuel storage in a common rail fuel injection system, it is necessary that the high-pressure accumulator on the one hand can be attached to the engine compartment, and on the other hand, the various supply and discharge lines for the fuel must be securely attached to the high-pressure accumulator. Here, the invention advantageously opens up the option of providing corresponding fastening devices for fastening the high-pressure fuel accumulator in the interior of the engine in the course of the casting on the outer jacket. Furthermore, precautions can be taken in the casting mold to form fastening elements for the fuel lines.

Further details, features, combinations and advantages based on the invention will become apparent from the following description of a preferred embodiment of the invention with reference to the drawings. These show in:

1a is an isometric view of a high-pressure fuel accumulator according to the invention.

1b shows a cross section through the high-pressure fuel accumulator from FIG. 1a.

FIG. 1a shows an isometric representation of a high-pressure fuel reservoir according to the invention. The cast body jacket 1 encloses the inner tubes 2 (longitudinal tube) and 3 (cross tubes). In the area of the transition between the cross tube and the longitudinal tube casing, fastening options 4 are provided for the fuel inlets and outlets. The high-pressure fuel accumulator according to the invention can be fastened in the engine compartment with the fastening tabs 5.

Figure 1 b shows a longitudinal section through the high-pressure fuel accumulator from Figure 1a. The course of the inner tubes 2 and 3 and the sheathing thereof with the cast body jacket 1 is shown. The profile of the inlet or outlet attachment 4 can also be seen in section. The inner tube wall 6 has a wall thickness in relation to the outer jacket wall 7 which is in the range between 1: 5 and 1:15. The outer shell is reinforced in its wall thickness 8 in the area of the fuel inlets and outlets.

LIST OF REFERENCE NUMBERS outer sheath

Inner longitudinal tube Inner cross tubes

Fastening for fuel inlet and outlet lines

fixing laugh

internal tube wall,

Außenmantelwandung

Reinforcement of the outer jacket wall

Claims

claims

1. Line (1, 2, 3) for the storage of high-pressure fuel, oil or other liquids, for use in a common rail fuel injection system, with an outer jacket (1) which is made of cast material and is tubular, characterized in that inside one or more inner tube parts (2, 3) are arranged on the outer shell (1), and the outer shell (1) is formed by encapsulation or injection molding around the one or more tube parts (2, 3).

2. Line (1, 2,3) according to claim 1, characterized in that the outer jacket (1) consists of several layers, which are formed by encapsulation or overmolding of the one or more pipe parts (2,3).

3. Line (1, 2,3) according to claim 2, characterized in that the

Layers of the outer jacket (1) consist of different materials and / or material qualities.

4. Line (1, 2, 3) according to one of claims 1 to 3, characterized by a line structure composed of the outer jacket (1) and the pipe part (s) (2,3), the outer jacket (1) and / or the or the pipe parts (2, 3) are made with metal.

5. Line (1, 2, 3) according to one of claims 1 to 3, characterized by one of the outer jacket (1) and the one or more inner tube parts

(2,3) composite pipe structure, the outer jacket (1) and / or the pipe part (s) (2,3) being made of plastic or other non-metallic material or with a mixture of metallic and non-metallic material.

6. Line (1, 2,3) according to one of the preceding claims, characterized in that the outer jacket (1) with graphitic cast iron, in particular the spheroidal graphite cast iron GGG 40, or another cast iron is produced.

7. Line (1, 2,3) according to any one of the preceding claims, characterized in that the one or more pipe parts (2,3) separately from

Outer jacket (1) are formed and / or made with stainless steel, stainless steel, ceramic and / or glass.

8. Pipe (1, 2, 3) according to one of the preceding claims, characterized in that the plurality of pipe parts (2, 3) have a longitudinal pipe (2) that defines a longitudinal direction of the pipe, and one or more to the longitudinal pipe (2 ) attached cross tubes (3).

9. Line (1, 2, 3) according to claim 8, characterized in that the tube parts (2, 3) are connected to one another by soldering or welding.

10. Line (1, 2, 3) according to claim 8, characterized in that the tube parts (2, 3) are made in one piece with one another.

11. Line (1, 2, 3) according to claim 8, 9 or 10, characterized in that the outer jacket (1) is reinforced in the region of the transition or transitions between the inner longitudinal tube (2) and the inner cross tube (s) (3) is executed.

12. Line (1, 2,3) according to claim 11, characterized in that this reinforcement is realized by increasing the wall thickness of the outer jacket (1).

13. Line (1, 2,3) according to one of claims 8 to 12, characterized in that the cross section of the inner longitudinal tube (2) in

Circular, polygon, ellipse or free form is formed.

14. Line (1, 2, 3) according to one of claims 8 to 13, characterized in that the cross-sectional shape and / or the cross-sectional area of the inner longitudinal tube (2) changes in the course of the longitudinal axis of the tube.

15. Line (1, 2, 3) according to one of the preceding claims, characterized by a ratio of the wall thicknesses of the inner tube part or parts to the wall thickness of the outer jacket, which is between 1: 5 and 1:15.

16. Line (1, 2, 3) according to one of the preceding claims, characterized by a ratio of the wall thicknesses of the inner tube part or parts to the wall thickness of the outer jacket, which is between 1: 8 and 1:12.

17. A method for producing a line (1, 2,3), in particular according to one of the preceding claims, for the storage of high-pressure fuel, oil or other liquids, for use in a common rail fuel injection system, wherein by casting a tubular outer jacket (1) is formed in the molten or liquefied cast material, characterized in that one or more inner tubular parts (2, 3) are arranged, which are then encapsulated and / or extrusion-coated with the cast material.

18. The method according to claim 17, characterized in that the one or more inner tube parts (2, 3) are overmolded and / or overmolded with a plurality of layers of the same, similar and / or different casting materials.

19. The method according to claim 17 or 18, characterized by the

Use of metal or metal-provided material for producing a line (1, 2,3) composed of an outer jacket (1) and one or more pipe parts (2, 3).

20. The method according to claim 17 or 18, characterized by the use of plastic or other non-metallic material or of a mixture or a combination of metallic and non-metallic material for the production of an outer jacket (1) and one or more pipe parts (2, 3) Line (1, 2,3).

21. The method according to any one of claims 17 to 20, characterized by the use of stainless steel, stainless steel and / or ceramic for the one or more pipe parts (2,3).

22. The method according to any one of claims 17 to 21, characterized by the use of graphitic cast iron, in particular spheroidal graphite cast iron GGG 40, or other cast iron for the outer jacket (1).

23. The method according to any one of claims 17 to 22, characterized in that the pipe part (s) (2, 3) are initially formed separately, then connected to one another and arranged in a casting mold and cast or extrusion-coated with the casting material.

24. The method according to any one of claims 17 to 23, characterized in that an inner longitudinal tube (2) made of a plastically deformable material, in particular steel, before being connected to the further inner tube parts (3) by mechanical processing in its

Cross-sectional shape is transformed from an original circular shape into an elliptical or other cross-sectional shape.

25. The method according to claim 24, characterized in that the inner longitudinal tube (2) is formed by the following steps: • insertion of a dome with the desired cross-sectional shape into the tube interior; • Forming the tube to the desired cross-sectional shape by means of pressing, cold drawing and / or hot drawing; • Remove the dome from the inside of the pipe.

26. The method according to any one of claims 23 to 25, characterized in that an inner longitudinal tube (2) made of a plastically deformable material, in particular steel, before connecting to the other inner tube parts (3) by mechanical processing in some areas in its cross-sectional area and / or shape is changed.

27. The method according to claim 26, characterized in that the inner longitudinal tube (2) is formed by the following steps: • insertion of a dome into the areas of the tube interior which are to be changed in their cross-sectional shape and / or area; • Forming the tube area into the desired cross-sectional shape by means of pressing, cold drawing and / or hot drawing; • Remove the dome from the inside of the pipe.

28. The method according to any one of claims 17 to 27, characterized in that in the course of casting on the outer jacket (1) connection devices (4) for motor vehicle cylinders and / or line attachments are formed.

29. The method according to any one of claims 17 to 28, characterized in that in the course of casting on the outer jacket (1) connecting devices (5) are formed for fastening the line in the engine compartment.