EP2466116B1 - Pulsation dampener - Google Patents

Description

The invention relates to a device for injecting a pressurized fuel fluid into a combustion chamber with a pressure generator, at least one injector with injection opening and a fuel line between the pressure generator and the injector according to the preamble of claim 1.

Such devices are used, for example, in internal combustion engines in which clocked under high pressure fuel and metered into the combustion chamber of individual cylinders is injected. Particularly in this application, very short switching times of the injectors and an accurate volume metering of the fuel are advantageous.

By switching the injectors pressure pulses are generated, which lead to undesirable vibrations in the fuel in the fuel line and can interfere with the metering of the fuel both over time and in terms of the amounts to be metered.

For this purpose, pulsation dampers for fuel in fuel supply systems of an internal combustion engine have already become known, as for example in the DE 195 16 358 C1 are described.

In addition, for example, from the DE 102 47 775 B4 . DE 10 2006 054 178 A1 or US 4,356,091 Damping elements or filters known, which are formed, inter alia, as a sintered material, metal strips, fibers, tube bundles or fabric.

However, it has been found that hereby the damping can be attenuated on the one hand only in a specific, narrow frequency range. On the other hand, the occurring pressure pulsations or pressure waves can generally be damped only unsatisfactorily. Thus, a very exact dosage of the injection, especially for several, short-term and shortly after one another taking place injection phases with very small amounts only partially possible. This leads to a non-optimal combustion with correspondingly increased fuel consumption and adverse pollutant emissions.

Object of the present invention is therefore to provide a device according to the preamble of claim 1 with an improved damping.

This object is achieved in each case by the features of the independent claims. The features mentioned in the dependent subclaims advantageous embodiments and refinements of the invention are possible.

Accordingly, a device according to the invention is characterized in that at least two different damping elements are provided, wherein the first damping element has at least a first material and / or a first structure and wherein the second damping element at least a second, the first different material and / or a second , to the first has different structure.

With the help of the invention, different damping principles or mechanisms can be used together in an advantageous manner. Thus, two or more different damping elements can complement each other in a special way or synergy effects can be realized in order to optimize the damping effect and / or the avoidance of pressure losses in the flow direction behind the damping elements or the damping unit. So at least a two-stage or three-stage damping be realized.

Preferably, at least one spacer element is provided for defining the distance and / or the volume of the intermediate space between the two damping elements. Hereby, the size of the gap or the distance can be set exactly or fixed in particular force-locking. This is advantageous for e.g. to promote or generate the formation of standing waves and / or reflections in the gap. Thus, a structural unit or damping unit can be provided with at least two damping elements, wherein between the damping elements, the spacer element is arranged and / or wherein a common sleeve or the like determines the distance between the damping elements or defined.

Basically, according to the invention, for example, superposition effects or interferences can advantageously be combined with frictional effects, turbulences or with dissipation or the like, or be used in a complementary manner or even reinforcing each other.

This advantageous effect or effects are enhanced or optimized in that according to the invention between the two damping elements in an advantageous manner, a boundary zone or a transition region, in particular with an effective or effective interface and / or reflection surface is generated, the / a generated to the damping effects of the two damping elements, further or third damping effect. This can be realized, for example, in that two adjacent damping elements each have a contact or contact surface. This means that in this variant of the invention, these two damping elements directly abutting or touching each other or are formed standing in contact with each other.

By forming this effective border zone or the transition region between two adjacent Damping elements is already a three-stage damping can be realized.

Alternatively or in combination with the aforementioned variant with direct contact of the damping elements, in a further embodiment of the invention, at least two mutually spaced damping elements can be provided, between which a gap is arranged. Under certain circumstances, standing waves and / or reflections and / or calmer flow conditions may advantageously form in this intermediate space. The combination of the aforementioned variants is e.g. formed by curved perforated sheets, metal mesh or the like, for example, the circumference or centrally touch, but on each other surfaces (slightly) spaced and herein include a gap or cavity.

Preferably, at least one spacer element is provided for defining the distance and / or the volume of the intermediate space between the two damping elements. Hereby, the size of the gap or the distance can be set exactly or fixed in particular force-locking. This is advantageous for e.g. to promote or generate the formation of standing waves and / or reflections in the gap. Thus, a structural unit or damping unit can be provided with at least two damping elements, wherein between the damping elements, the spacer element is arranged and / or wherein a common sleeve or the like determines the distance between the damping elements or defined.

In elaborate experiments, it has been found that, in particular, the size of the volume of the intermediate space with respect to the damping effect is advantageous. Preferably, the intermediate volume is substantially between 1 and 10 cubic centimeters in size. In order to do justice to the cramped space conditions, for example in vehicle, in particular automotive applications, the volume of the intermediate space is as small as possible or substantially 1 cubic centimeter in size. Hereby can comparatively small dampers can be achieved with quite good damping effects. In particular, injectors or damping units which are relatively small and can also be accommodated well in modern vehicles with limited space can be realized.

In an advantageous embodiment of the invention, at least one of the damping elements comprises a bundle of elongated elements, which comprise advantageous flow channels for partial flows of the fuel fluid as hollow bodies and / or through spaces between hollow bodies and / or solid bodies.

Advantageously, at least one of the damping elements comprises a pore-forming material, in particular a sintered material, foam material, fiber material such as fleece or fabric, a bed of loose and / or at least partially fixed or glued to each other, welded individual bodies, or the like.

By using a pore-forming material, there is an energy dissipation in the flow of the fuel fluid which is due to different effects, e.g. based on friction, throttling, etc. Pore-forming material, for example, increases the contact area of the fuel fluid with the surrounding material, resulting in significantly increased friction. In addition, a throttling effect and turbulences are achieved by a cross-sectional reduction. These and other processes provide e.g. for the desired energy dissipation, which dampens in a vibrating system.

Such a damping element according to the invention can be realized in different ways. Thus, for example, a chamber may be provided which is filled with pore-forming material, which is held together by suitable retaining elements, for example by sieves or the like in the chamber.

Another possibility is from the pore-forming Material to produce a body by the material is bonded, so that no outer wall is required to hold the pore-forming material in the form.

In a variant of a damping element, for example, a chamber can be filled with bulk material, whereby a damping element can be realized in a simple manner. As bulk material is for example a fiber material or the like in question. In this case, a single type of material or a mixture of different materials can be used. Different particle sizes can also be used depending on the application in a mixture of bulk material.

As a fiber material for filling a chamber, for example, structures made of metal fibers, such as steel wool or the like are conceivable, which can bring about the desired energy dissipation and, moreover, in an environment with very harsh operating conditions in terms of temperature, pressure or the like.

In another embodiment with bonded porous material, different bodies are also usable. For example, a porous sintered body in which a granular material or granules are bonded to a body under a high pressure and at a high temperature can be used. Another variant is to glue corresponding particles or grains together by introducing a corresponding adhesive as a binder in the formation of the body. It is also possible to produce a felt body with fiber material which can likewise provide the dissipation according to the invention. An open-pore foam can also be used, for example, as a damping body according to the invention. In particular, metal foams which have similar properties to sintered bodies are also suitable here.

Preferably, at least one of the damping elements comprises at least one perforated plate and / or at least one braid and / or a unit having multiple, contiguous or interlaced strands, such as a woven, braided, mesh, mesh, screen or the like.

The individual elements of a damping element such as tubes, rods, wires, braids, sheets or layers may be loosely and / or at least partially bonded or fixed, e.g. Spot welded, glued, soldered, etc., so that no outer wall is required to hold the Dämfungselement or a stack of these individual elements or damping layers in the form and / or installation.

Preferably, at least one of the damping elements comprises at least one stack with a plurality of perforated plates designed as damping layers and / or a plurality of braids and / or a plurality of units having the strands.

In general, a single type of material or a mixture of different materials can be used for a damping element according to the invention. Also, different structures or individual elements such as sintered material, tube bundles, tissue and / or fiber / wire sizes can be used depending on the application in a conglomerate, mixture or a single damping element according to the invention.

As fiber material for the metal ropes or lices, for example, metal fibers such as (high-grade) steel, brass, copper wire or corresponding wire ropes or the like are conceivable. Corresponding materials can also be used or combined for the wires or perforated plates. On the one hand, the desired energy dissipation can be effected hereby or, on the other hand, in an environment with very harsh operating conditions with regard to temperature, pressure or the like, these materials or embodiments can be used in an advantageous manner.

In a further embodiment with at least one perforated plate and / or at least one braid and in addition In addition, different bodies can be used with a bound porous material, so that different structures are advantageously produced. For example, a porous sintered body in which a granular material or granules are bonded to a body under a high pressure and at a high temperature can be used. Another variant is to glue corresponding particles or grains together by introducing a corresponding adhesive as a binder in the formation of the body. It is also possible to produce a felt body with fiber material, which likewise can provide the damping or dissipation according to the invention. An open-pore foam can also be used, for example, as a damping body according to the invention. In particular, metal foams which have similar properties to sintered bodies are also suitable here.

In a particular embodiment of the invention, a cross-sectional diameter of the cross-sectional area and / or a pore diameter of the pores is substantially between 10 and 100 micrometers, preferably between 10 and 50 micrometers in size. In countless experiments and extensive simulations, it has surprisingly been found that such a length of the damping element is an optimum with respect to the conflicting requirements such as (maximum) damping effect, (lowest possible) pressure reduction and (as little as possible) space requirements. The first two requirements are particularly important in terms of the exact and effective fuel management is essential.

The latter requirement is of particular relevance for vehicle applications, in particular for automotive applications. In order to do the cramped space conditions, for example in vehicle, in particular automotive applications, the construction volume of the device or damping unit or injector according to the invention is to be realized as small as possible. According to the invention comparatively small dampers can be realized with quite good damping, too to be accommodated in modern vehicles with limited space.

According to the invention, a cross-sectional diameter of the cross-sectional area and / or a pore diameter of the pores is substantially between 5 and 200 microns in size, preferably substantially between 10 and 100 microns in size. Again, it has been shown in numerous experiments that these size ranges are of particular advantage in order to meet the diverse and sometimes conflicting requirements (see above).

A significantly improved compared to the prior art damping is achieved in that a ratio of a cross-sectional diameter of the cross-sectional area and / or a pore diameter of the pores to aligned in the direction of flow of the fuel fluid length of the damping element is substantially between 2 and 5 microns per millimeter.

In particularly preferred embodiments of the invention, for example, a cross-sectional diameter of the cross-sectional area and / or the pore diameter of the pores is substantially 10 micrometers and the length of the damping element aligned in the flow direction of the fuel fluid is substantially 2 millimeters. On the other hand, for example, a cross-sectional diameter of the cross-sectional area and / or a pore diameter of the pores is substantially 100 micrometers and the length of the damping element aligned in the flow direction of the fuel fluid is substantially 50 millimeters. These dimensions have been highlighted in the experiments.

A volume of the gap / area between two damping elements can be formed> 0.5 cm ³ , for example, from about 1 cm ³ to 2 cm ³ has already proved to be particularly advantageous.

By adjusting the volume and / or the length and the cross section of the intermediate area between the Damping elements, the damping effect can be positively influenced. In particular, it is possible to tune to natural or resonant frequencies of the pulsations.

In principle, an arrangement of a damping element according to the invention in the vicinity of an injector or even in the injector makes sense, in order to introduce the damping effect in the immediate vicinity of the place of origin of the pulsation. However, it is advantageous to construct the damping element at an upstream position with respect to the flow direction of the fuel fluid, since in the area of the injectors there is often an extreme lack of space, difficult accessibility and / or other unfavorable conditions.

In addition, in particular in internal combustion engines usually multiple injectors are used to supply different cylinders with fuel. Frequently, a common fuel line is used, which has branches or branch lines for supplying a plurality of injectors. Furthermore, in such devices often a main line is provided, branch off from the at certain intervals branch lines to different injectors. This arrangement corresponds for example to the construction of so-called common rail injection systems.

The arrangement of damping elements or damping units according to the invention is, as stated above, advantageous in the region of branch lines of the fuel supply, wherein in the region of the branch lines due to the external conditions and the dimensions of the installation is more difficult to implement and also the damping acts directly on all injectors.

On the other hand, the entire system can be largely decoupled from the pulsations caused by a specific injector by damping in the region of the branch lines. Therefore, depending on the application, it may also be particularly advantageous, especially in such a branch line Pre-allocate one or more damping elements directly to an injector.

In another embodiment of the invention, one or more damping elements can be arranged in an unbranched region of the fuel line behind the pressure generator. This arrangement has the advantage that, with the same damping elements, the pressure pulsations caused by all the injectors can be damped according to the invention. In addition, the fuel line in this area is generally more accessible and usually has a larger cross section in this area. Accordingly, one or more damping elements can be accommodated more easily in this area of the fuel line.

Advantageously, a damping unit can be formed from one or more damping elements. This can be used in an advantageous manner as a whole, for example via end connection elements, such as connecting flanges or the like in the fuel line. But such a damping unit can also be designed as an insert or as a separately manageable unit, which is / can be mounted in an advantageous manner in the fuel line or can be inserted.

In the case of a main line as stated above, a damping unit can also be integrated into this main line, in turn, a damping unit is conceivable, which is introduced via terminal connection elements in the fuel line or inserted as a slot in the main line.

In particular, in the arrangement as a drawer or as a separately manageable unit, the damping unit can also be formed so that between two or more branch lines in the main line one or more damping elements are arranged so that it is ensured that between two or more injectors each one Damping element is arranged and a direct pulse transmission between injectors is suppressed without damping element.

A damping unit with a plurality of damping elements is preferably formed so that a flow zone results between the individual damping elements, in which the partial flows are at least partially reunited.

When using a plurality of damping elements according to the invention, all damping elements of the same type, i. only one material or only a single structure / type However, the advantageous use of (completely) differently structured or structured damping elements is of particular advantage.

In an advantageous development of the invention, a fuel filter is additionally provided in the flow direction in front of at least one damping element. Preferably, the fuel filter is mounted in front of the first flow-through damping element in order to retain or remove disturbing particles or contaminants before they pass into a damping element. As a result, the risk of clogging a damping element is reduced or completely avoided. In principle, such a fuel filter can also already be arranged upstream of the pressure generator in the flow direction.

Furthermore, a pulsation damping according to the invention can advantageously be combined with one or more surge tanks. One or more surge tanks communicating with the fuel line can provide as constant a pressure as possible in the fuel line. Such surge tank, which usually have a membrane or a piston which separates liquid and thus largely incompressible pressurized fuel fluid from a chamber in which a compressible medium, usually a gaseous fluid, such as air or the like pressurized can be arranged, for example, fluctuations compensate for a fuel pump. In addition, such a surge tank can further improve the pulsation damping.

The damping according to the invention can be further improved by, on the one hand, lengthening the flow path of the fuel fluid in the damping body and / or, on the other hand, reducing the pore size. As a result, the desired damping or energy dissipation is increased. Preferably, accordingly, average pore sizes of less than 80 μm, preferably less than 40 μm, are selected.

An embodiment of the invention is illustrated in the drawing and will be explained in more detail with reference to FIGS.

Figur 1

eine schematische Darstellung einer Brennstoffleitung für einen Verbrennungsmotor,

Figur 2

eine schematische Darstellung einer erfindungsgemäßen Dämpfungseinheit mit zwei Dämpfungselementen,

Figur 3

eine schematische Darstellung eines Teilausschnitt eines Dämpfungselementes,

Figur 4

eine weitere Ausführungsvariante eines Dämpfungselementes zur Verwendung in einem Injektor,

Figur 5

eine schematische Darstellung eines Injektors mit Dämpfungselement,

Figur 6

eine weitere Ausführungsvariante eines Dämpfungselementes,

Figur 7

eine Schemadarstellung eines Common-Rail-Systems mit zwei Injektoren vorgeordneten Dämpfungselementen,

Figur 8

eine schematische Darstellung eines als mehrschichtiger Stapel ausgebildetes Dämpfungselementes in zwei Varianten,

Figur 9

mehrere schematische Querschnitt-Darstellung von verschiedenen Dämpfungselementen,

Figur 10

zwei schematische Darstellungen von Druckverläufen mit und ohne Dämpfungselement und

Figur 11

schematische Darstellungen von verschiedenen Auswirkungen von Druckpulsationen auf eine Einspritzmenge in Abhängigkeit der Zeit.

In detail shows

FIG. 1

a schematic representation of a fuel line for an internal combustion engine,

FIG. 2

a schematic representation of a damping unit according to the invention with two damping elements,

FIG. 3

a schematic representation of a partial section of a damping element,

FIG. 4

a further embodiment of a damping element for use in an injector,

FIG. 5

a schematic representation of an injector with damping element,

FIG. 6

a further embodiment of a damping element,

FIG. 7

a schematic representation of a common rail system with two injectors upstream damping elements,

FIG. 8

2 is a schematic representation of a damping element designed as a multilayer stack in two variants,

FIG. 9

several schematic cross-sectional representation of different damping elements,

FIG. 10

two schematic representations of pressure gradients with and without damping element and

FIG. 11

schematic representations of different effects of pressure pulsations on an injection quantity as a function of time.

A fuel line 1 according to FIG. 1 comprises a main line 2, branch off from the various branch lines 3.

Each branch line 3, 4, 5, 6 serves to supply fuel to an injector of an internal combustion engine. The main line 2 can be extended at its end no longer shown in the drawing, so that any further number of branch lines can follow.

In each branch line 3, 4, 5, 6, a damping element 7, 8 is used, which is flowed through by the fuel stream. Due to the advantageous, in particular (different) stacked construction of the damping elements, the o. A. Energy dissipation and thus also the particularly advantageous pulsation damping allows.

In the main line 2 is additionally a damping unit 11, which is inserted into the main line 2. Especially in FIG. 2 becomes clear for such a unit or damping unit 11, that these in an advantageous Can be handled separately and, for example independently of other components can be tested or tested and finally installed in the Brennstpoffsystem pre-assembled and mounted and possibly dismantled or replaced again if necessary. Here are not only a total length L _{D of} the damping unit 11, 21, but above all, a distance A between two adjacent damping elements or stack 17, 18, 19, 20 and thus at a given pipe inner diameter of the assembly 11, 21 corresponding to a distance volume V exactly adjustable. This is for the attenuation and the adjustment of the frequencies to be attenuated or the frequency spectrum to be attenuated of particular importance. Also, a diameter D (see. FIG. 3 ) of openings 28 and pores 28 and capillaries 28 for the damping effect of importance.

In a further variant of the invention, e.g. certainly also three or four damping elements 17, 18, 19, 20 are integrated or mounted in a damping unit 11, 21.

Preferably, the total length L _{D of} the damping unit 11, 21 is twice as long as the length of the interior space from an injector nozzle to the injector outlet. The volume V is (at least) about 1 cubic centimeter in size. A length L of the damping element or stack 17, 18, 19, 20 is preferably about 2 to 50 millimeters in size.

The damping unit 11 according to FIG. 1 comprises an axially flow-through pipe, which is separated at different points, so that at these points, a radial flow is possible. Shown in the tube 12 of the damping unit 11 by way of example three radial openings, which serve the inflow or outflow of fuel fluid. The radial openings 13, 14, communicate with the branch lines 5, 6, so that fuel fluid from the interior of the tube 12 of the damping unit 11 can flow in these branches in the radial direction.

The radial opening 15 is in communication with a Supply line 16 which is connected to a pressure generator, not shown.

In the tube 12 of the damping unit 11 are two damping elements 17, 18, which are preferably constructed as a stack 20 of a plurality of perforated plates 48 and / or (ordered) braid layers or fabric layers 47. In FIG. 8 is schematically illustrated such a layering in two different variants. In FIG. 8a an ordered layering of eg perforated plates 48 or fabrics 47 is shown. Here, the openings 28 or pores 28 are arranged substantially one above the other or in such a way that (almost rectilinear) channels are generated. In FIG. 8b By contrast, the layers or layers or damping layers are arranged offset (transversely) in such a way that the fuel fluid does not have to flow through in a straight line, but rather through a very branched pore system through the damping element or the stack 20. Accordingly, the effective channel path increases in comparison to the straight-line flow according to FIG FIG. 8a ,

In the FIG. 1 shown arrangement of damping elements can be used for example in a so-called common rail system. The fuel is fed via the pressure generator through the supply line 16 into the main line 2 and can propagate there in both axial directions of the main line 2. The fuel flows through a respective damping element 17, 18, wherein the energy dissipation occurs and pulsations are damped.

From the main line 2 branch off branch lines 3, 4, 5, 6, which serve to supply fuel fluid to the individual injectors or cylinders of an internal combustion engine. The damping elements 7, 8, 9, 10 in these branch lines 3, 4, 5, 6 are in turn stacked according to the invention and in particular stacked to cause the energy dissipation, which acts to damp pulsations.

In the embodiment according to FIG. 1 are both in the Main line as well as housed in the branch lines damping elements. Since the fuel supply is to be regarded as an overall system, depending on the application, a sufficient damping can already be achieved with arrangements in which damping elements are arranged only in the main line or only in the branch lines.

FIG. 2 shows a variant in which a damping unit 21 is inserted as a slot in a fuel line 22, comprising two damping elements 23, 24, between which a gap 25 is formed as a flow zone without a perforated plate and / or a braid / fabric. In the damping elements 23, 24 of the stack 19, 20 is indicated from a plurality of perforated plates and / or braid / fabric layers. The damping elements 23, 24 are mounted in a support tube 26, so that the damping unit 21 can be handled as a complete unit.

A damping unit according to FIG. 2 For example, instead of the damping elements in FIG. 1 be used. The combination of two damping elements 23, 24 with the intermediate space 25 has already shown an improved damping effect compared to the pure accumulation of the damping effect of the individual damping elements 23, 24. The execution according to FIG. 2 can be further expanded to the effect that further damping elements and other spaces are combined in one unit.

FIG. 3 shows a section of a Lohblech 27 with a circular cross section, wherein numerous holes 28 are provided. These holes 28 can be drilled, stamped, lasered or made comparable. As a stack 20 (see, eg Fig. 4 ) is advantageous if the holes 28 are at least partially offset in the transverse direction to the perforated plate 27 and to the flow direction of the fluid or overlap only partially.

FIG. 4 shows a principle according to the embodiment according to FIG. 2 corresponding variant of a damping element 29 with a multi-layer stack 20. The damping element 29 is used directly in an injector. For this purpose, a large central bore 30, which can be penetrated by a needle of a needle valve of an injector.

FIG. 5 shows a schematic representation of such an injector 31. The injector 31 shows a nozzle housing 32 with a nozzle opening 33. In the interior of the nozzle housing 32 is a fuel line 34 into which a damping element 29 according to FIG. 4 is used. The damping element 29 is penetrated by a nozzle needle 35 which can seal with its tip 36 with respect to a valve seat 37 and thereby closes or opens the nozzle opening 33. The injector can control the injection process by axial movement of the nozzle needle 35 both in terms of the time course and thereby also with regard to the injected fuel volume.

Also in the execution according to the FIGS. 4 and 5 the fuel flow through the damping element 29 experiences an energy dissipation. The central bore 30 of the annular damping element 29 is thereby closed by the nozzle needle 35 so that only the path through stack 20 remains for the fuel fluid. As a result, the damping effect according to the invention is generated directly at the point of origin of the pulsation in the vicinity of the nozzle opening 33.

Also, such annular damping elements 29 may in multiple versions with gaps corresponding to the gap 25 according to the embodiment according to FIG. 3 can be used to further increase the damping effect.

FIG. 6 shows a further embodiment of a damping element 17, 18. It comprises a base body in which many small longitudinal bores 28 are mounted. The longitudinal bores 28 are formed continuously. In each longitudinal bore 28 may therefore form a partial flow, which contributes to the invention damping. In the FIG. 1 drawn damping elements, for example, with a damping element 17 according to FIG. 2 partly replaced or be used in combination.

FIG. 7 shows a schematic representation of a common rail system 38 with a commonly referred to as "common rail" main line 39, from the two branch lines 40, 41 depart in the illustrated case. The branch lines 40, 41 lead to injectors 42, 43. The injector 42 is in operation, as indicated by dashed lines, which are intended to represent sprays of injected fuel.

In the execution according to FIG. 7 It can be seen that damping units 45, 46 according to the invention are arranged upstream of the injectors 42, 43.

The damping units can be used as simple, preferably stacked or multi-layer damping elements, such as the damping element according to FIG. 4 or 6 or 8 or as a multi-stage, in particular two-stage damping unit according to the damping unit 21 according to the embodiment according to FIG. 2 be educated.

The arrangement of the damping units 45, 46 leads as well as an integration of a damping element in the injector, as in the embodiment according to FIG. 7 is provided with the damping element 29, to the fact that pulsations that are triggered by an injector, can be largely decoupled from the overall system. In the arrangement according to FIG. 7 the injector 42 is active, ie it triggers corresponding pulsations, which are, however, largely attenuated in the damping unit 45, so that the total system located upstream of the damping unit 45 in the flow direction is largely uncoupled from the pulsations of the injector 42. This means that in the temporal sequence of the injector 43 can be operated without being affected by previously caused by the injector 42 pulsations. As a result, a more accurate metering of fuel, in particular with regard to the injection pressure and the metered amount is possible.

In addition to the described embodiments are still many other versions of the invention damping elements and damping arrangements possible. A construction according to FIG. 3 can also be achieved with flexible fibers, both variants with fibers of solid material and hollow fibers are conceivable. These are in FIG. 9 further variants shown.

In the FIG. 9 Variants shown, for example, have individual openings 28 or capillary 28 or channels 28, which can also be joined together to capillary bundles. The capillary is produced by mechanical processing (eg drilling, erosion, lasers), by forming (for example, large tubes are rolled and drawn until they reach the desired diameter), are urformed (eg production by casting, injection molding) or built (Eg by layers of several perforated plates / sheets). The individual capillaries 28 can be connected to one another to form a bundle by being welded or glued to the contact surfaces ( FIG. 9 a) or with a fuel-resistant material 99 (Ex: PPE, Lauramid) are cast ( FIG. 9 b) , A carrier sleeve 12 or tube 12 (FIG. FIG. 9c) in which the individual capillary 28 or tubes 28 are introduced, can also be used. The volume can be adjusted in special cases by a spacer sleeve.

Likewise, to generate capillaries 28 or capillary bundles, a bundle of solid tubes or wire 98 or the like (US Pat. FIG. 9 d) be used.

Also, holes 28 can be etched in plates 27 to produce perforated plates, which then stacked on each other in an advantageous manner, possibly again give a capillary bundle. Also, long channels / lines can be etched along the surface of a plate. If you place two of these plates with the etched side together, you will also get capillaries. So are also different combinations of manufacturing processes mutually conceivable for the production of capillaries. For example, capillaries can be generated by nanotubes and microstructures.

The advantageous diameter of a pore or capillary is 10 .mu.m-40 .mu.m in order to advantageously avoid contamination or clogging and to achieve good damping.

In principle, according to the invention, both similar, preferably (differently) stacked and different damping elements, e.g. Fabric combined with grid and / or tube bundle or perforated sheets, combined in one device.

Of particular advantage is the construction according to the invention e.g. with (different) perforated plates and / or mesh / fabric layers of the damping element, whereby the damping effect is significantly improved compared to previous throttle devices.

According to the invention, an advantageous damping of the pulsation vibrations, which are generated when the injector is closed, is achieved. This is in FIG. 10 something illustrated. FIG. 10a shows a Durckverlauf without damping elements and FIG. 10b with damping.

The fast closing of the injector after the injection process generates pressure pulsations ( FIG. 10a ). These are transmitted by the fluid in the rail or pipe. If several injectors are connected to the same line or rail, they also experience the pressure pulsations from the closing injector. The generated pressure pulsations behave similarly to a sinusoidal oscillation. Depending on the time interval, a wide variety of pressures are thus present in front of the injector injector, which results in an exact, reproducible minimum quantity injection makes it impossible to reduce pollutant emissions ( FIG. 11 ).

An advantageous damping element preferably between the pressure generator and the injection opening of an injector is provided according to a variant of the invention in an advantageous manner, wherein the fuel flow is divided by the damping element, esp. By the tissue pores and / or holes of the perforated plates in a plurality of partial streams and wherein in the flow direction behind the damping element, the partial flows are at least partially reunited. By dividing the total flow of the fuel quantity into partial flows, an increased energy dissipation is realized in the damping element, which can be based on different effects. In particular friction and throttle effects play a role. Thus, for example, the contact area and the contact time of the fuel fluid with the wall regions of the damping element and thus also the friction are significantly increased by the inventive division of the total flow of the fuel fluid. Due to the increased energy dissipation can be a pulsation, which is caused for example by the switching of an injector, effectively dampen. As a result, improved metering of the fuel is possible both in terms of timing and in terms of the amount to be metered. Through a reproducible injection (even small-quantity injection), the pollutant emissions are reduced and the combustion process improves.

Advantageously, a damping element or a damping unit which / divides the fuel into a plurality of partial flows and reunited after the damping element and / or at least two mutually spaced damping elements are provided, wherein There is a flow zone between them in which the partial flows reunite. Also advantageous are damping units with combinations of ordered wire mesh and / or bulk material and / or wire mesh, in this case, the number of any layer / layer can be varied as desired.

LIST OF REFERENCE NUMBERS

1

fuel line

2

main

3

branch line

4

branch line

5

branch line

6

branch line

7

damping element

8th

damping element

9

damping element

10

damping element

11

damping unit

12

pipe

13

radial opening

14

radial opening

15

radial opening

16

feed pipe

17

damping element

18

damping element

19

stack

20

stack

21

damping unit

22

fuel line

23

damping element

24

damping element

25

gap

26

support tube

27

perforated sheet

28

holes

29

damping element

30

central bore

31

injector

32

nozzle housing

33

nozzle opening

34

fuel line

35

nozzle needle

36

pinpoint

37

valve seat

38

Common rail

39

main

40

branch line

41

branch line

42

injector

43

injector

44

spray

45

damping unit

46

damping unit

47

tissue

48

perforated sheet

98

wire

99

material

Claims (13)

1. A device for injecting a combustible fluid which is under pressure in a combustion chamber having a pressure generator, at least one injector (31, 42, 43) with an injection opening (33) and a fuel line (1 to 6, 39 to 41) between the pressure generator and the injector (31, 42, 43), wherein in the direction of flow of the combustible fluid at least a first and a second attenuator are arranged one after the other for the reduction of combustible fluid-pressure waves between the pressure generator and the injection opening (33) of the injectors (31, 42, 43), wherein each of the attenuators (7 to 11, 23, 24) comprises several flow paths with average cross-sectional area, which can be freely flowed through, having a cross-sectional diameter and/or pores which can be freely flowed through, having a pore diameter, characterized in that at least two different attenuators (7 to 11, 23, 24) are provided, wherein the first attenuator (7 to 11, 23, 24) has at least a first material and/or a first structure and wherein the second attenuator (7 to 11, 23, 24) has at least a second material different from the first and/or a second structure different from the first.
2. A device according to claim 1 characterized in that at least three attenuators (7 to 11, 23, 24) are provided, wherein the third attenuator (7 to 11, 23, 24) has at least a third, material different from the first and/or from the second and/or a third structure different from the first and/or from the second.
3. A device according to one of the aforementioned claims characterized in that at least two attenuators (23, 24) are provided spaced apart from each other, between which an intermediate space (25) is arranged.
4. A device according to one of the aforementioned claims, characterized in that the intermediate space is essentially between 1 and 10 cubic centimeters In size.
5. A device according to one of the aforementioned claims, characterized in that at least one of the attenuators comprises a bundle of elongated elements (27), which as hollow bodies and/or through spaces between hollow- and/or solid bodies comprise flow channels (28) for partial flows.
6. A device according to one of the aforementioned claims, characterized in that at least one of the attenuators (17, 18) comprises a pore-forming material (19, 20).
7. A device according to one of the aforementioned claims, characterized in that at least one of the attenuators (17, 18) comprises a perforated metal plate and/or at least a braid and/or a unit having several strands positioned next to each other or intertwined.
8. A device according to one of the aforementioned claims, characterized in that at least one of the attenuators comprises at least a stack with several perforated metal plates designed as attenuation layers and/or several braids and/or several units having the strands.
9. A device according to one of the aforementioned claims, characterized in that the length of the attenuator oriented in the direction of flow of the combustible fluid is essentially between 2 and 50 millimeters in size.
10. A device according to one of the aforementioned claims, characterized in that a cross-sectional diameter of the cross-sectional area and/or a pore diameter of the pores is essentially between 10 and 100 micrometers in size.
11. A device according to one of the aforementioned claims, characterized in that at least one attenuation unit, which can be managed separately, is provided with at least two attenuators (23, 24) spaced apart from each other, wherein an intermediate space (25) is arranged between the two attenuators (23, 24).
12. A device according to one of the aforementioned claims, characterized in that the attenuation unit, which can be managed separately, has at least one spacer for fixing the distance and/or the volume of the intermediate space (25) between the two attenuators (23, 24).
13. A device according to one of the aforementioned claims, characterized in that an attenuator upstream of the injector is provided.

Images