Patent Application
20110272495
The invention relates to a fuel injector, in particular a common rail injector, for injecting fuel into a combustion chamber of an internal combustion. Furthermore, the invention relates to an internal combustion engine having at least one fuel injector.
DE 10 2005 053 112 A1 describes a fuel injector which is assigned a sealing element with which the combustion chamber of an internal combustion engine is sealed off from the surroundings. The sealing element is secured by a securing element.
The outer geometry of known fuel injectors and in particular the outer geometry of the nozzle body projecting into the combustion chamber of an internal combustion engine is substantially identical in virtually all types and shapes of fuel injectors and is distinguished by a long shank which is installed in a corresponding receiving bore in the cylinder head of the internal combustion engine. The nozzle shank has direct contact with the internal combustion engine, i.e. it is acted upon by the combustion gases and the chemical and reactive intermediate and reaction products thereof, for example atomic hydrogen, in the annular space to the cylinder head. The nozzle body of known fuel injectors is clamped to a holding body (housing part) of the fuel injector by force being applied to a nozzle body shoulder by means of a nozzle clamping nut, in order to produce internal sealing forces against hydraulic leakages. The entire fuel injector is clamped into the cylinder head with an axial clawing force in order to seal off the combustion chamber from the surroundings. For this purpose, it is known to insert copper sealing disks having inner lugs for centering purposes. Rising injection and combustion pressures in future development generations, in particular in common rail injectors, which are under a permanent hydraulic internal pressure, require a rise in the sealing forces, which leads to high mechanical stresses in an upper region of the nozzle shank, in particular at the transition to the nozzle collar of the nozzle body.
The invention is based on the object of proposing a fuel injector, the nozzle body of which is better protected against chemical and reactive intermediate and reaction products of the combustion in the combustion chamber of the internal combustion engine. Furthermore, it is the object to specify an internal combustion engine having a fuel injector of this type. In particular, the nozzle body of the fuel injector should be protected against combustion products irrespective of a concentricity offset between the clamping nut and nozzle body.
The invention is based on the concept of protecting points of the nozzle body which are critical in terms of strength, in particular a transition region between a nozzle shank and a nozzle collar, against condensate and/or chemical and reactive intermediate and reaction products of the combustion by the provision of at least one seal. By the provision of a seal of this type which is designed and arranged to protect at least one nozzle body region which is critical in terms of strength, in particular as per the variant embodiments explained below, corrosion pits and hydrogen-induced “stress corrosion cracking” on the nozzle body, in particular on the nozzle shank, can be avoided. Without a seal of this type, these effects could ultimately lead to the nozzle body failing due to fracturing.
An embodiment of the fuel injector and of the internal combustion engine is very particularly preferred, in which the single-part or multipart seal is arranged at least partially axially between the nozzle body, preferably between the collar of the nozzle body and the clamping nut. In addition or as an alternative, the seal may be arranged at least partially axially between the clamping nut and the internal combustion engine.
In order to obtain an optimum sealing effect, it is preferred if the seal comprises an elastomer compound (elastic, preferably rubber-elastic sealing compound). By means of the elastic deformation during assembly of the fuel injector and/or during installation of the fuel injector into the internal combustion engine, an optimum, tolerance-insensitive sealing effect can be obtained by the elastic deformation of the sealing compound. A further advantage of providing an elastomeric sealing compound is that a captive function is achieved at the same time during the assembly by means of the high elastic radial forces with which the sealing compound is preferably supported on the nozzle shank of the nozzle body.
An embodiment is very particularly preferred, in which the elastic sealing compound is vulcanized onto a metal disk, in particular a copper disk, i.e. is connected fixedly and immovably to the metal disk. In this case, it is furthermore preferred if the elastic sealing compound bears radially on the nozzle shank of the nozzle body. It is furthermore preferred if the sealing compound additionally bears on the cylinder head or the nozzle body in the axial direction. The metal disk which is provided with the elastic sealing compound then not only has the task of sealing off the combustion chamber from the surroundings but also of producing gastightness between a shank step (transition region between the nozzle shank and nozzle collar) and the combustion chamber. As already indicated, it is preferred to arrange the elastomeric sealing compound on the inside diameter of the metal disk. For this purpose, the inner geometry of the metal disk is preferably correspondingly shaped, for example provided with a toothed profile, in order to achieve an improved connection between sealing compound and metal disk. During the assembly, the metal disk which is provided with the elastic sealing compound is preferably pulled in a self-centering manner onto a conical nozzle shank section and, by this means, is fully tolerance-insensitive in relation to the concentric offset between clamping nut and nozzle body.
As mentioned at the beginning, the sealing compound can be arranged in a radially and/or axially sealing manner. In the case of an axially sealing arrangement in which the sealing compound preferably bears directly on the internal combustion engine, in particular on the cylinder head, the sealing compound preferably comprises for this purpose an (axial) sealing lip which ensures that the combustion chamber is sealed off in a gastight manner from the surroundings.
In an alternative embodiment, the sealing compound is not vulcanized onto a metal disk but rather is formed as an independent component which is held in a form-fitting manner on the single-part or multipart metal disk, in particular copper disk.
A multipart design of the metal disk is preferred in this case, the (entire) metal disk preferably being formed by a plurality of metal disks arranged axially next to one another. For most application purposes, it will be sufficient to form the metal disk from two axially adjacent metal disks, wherein the metal disks form, on the inner circumference therebetween, a groove in which the elastomeric annular element is held. For different sealing disk thicknesses which are to be applied, it is possible to provide at least one further disk which preferably serves at the same time as a supporting disk for the elastomer ring (annular element).
In a further alternative embodiment, in which the elastic sealing compound is designed as an independent annular element, the latter can be held in an axial undercut of the nozzle collar of the nozzle body. In other words, a groove for holding an elastic annular element is provided on the end side of the nozzle collar. In this alternative, as a result of a suitable geometry of the undercut, the maximum mechanical stresses which occur in an upper region which is shielded from condensate and condensate products by the annular element, which is designed in particular as an O-ring. The required surface pressures in the undercut groove can be set in a specific manner by the high degree of accuracy of the annular element diameter (preferably O-ring diameter) and the undercut dimensions. It is thus possible to jointly grind the nozzle body shoulder (nozzle collar) and the groove on the end side into shape in one operation. The concentric offset of the nozzle clamping nut with respect to the nozzle body can be compensated for by an additional metal disk which is designed as a supporting disk, as a result of which the introduction of force into the annular element is homogeneous. A further advantage of the previously described alternative is that the additional metal disk, which acts as a supporting disk, can act on the intersection between the nozzle shoulder and clamping nut in a manner reducing the moment of friction.
In a further alternative embodiment, the seal is designed as a collar sleeve which is preferably free of elastomer compound, an embodiment also being conceivable, however, in which the collar sleeve is provided with elastomer material or interacts with an elastomeric element. During the manufacturing, a metallic and preferably corrosion-resistant collar sleeve is preferably pulled over the nozzle shank region which is critical in terms of strength and corrosion. The collar sleeve is preferably a shrink-on sleeve which is shrunk onto the nozzle shank. The collar sleeve can be designed, for example, as a cost-effective deep drawn part made of high-grade steel. As a result of the high degree of accuracy of the nozzle shank diameter, a robust oversize configuration is possible. A further advantage of this alternative is that the collar sleeve can act on the intersection between the nozzle body shoulder and clamping nut in a manner reducing the moment of friction.
Furthermore, the invention leads to an internal combustion engine having a previously described fuel injector, wherein the fuel injector is assigned a seal which is designed as previously described and provides protection against combustion products from the internal combustion engine for those regions of the nozzle body of the fuel injector which are at risk. Said region at risk is preferably a transition region between a nozzle shank and a nozzle collar of the nozzle body.
Further advantages, features and details of the invention emerge from the description below of preferred exemplary embodiments and with reference to the drawings, in which:
a shows a top view of the fuel injector according to
b shows an internal combustion engine with a fuel injector, wherein the fuel injector is assigned a seal which is arranged axially between a nozzle clamping nut and a cylinder head of the internal combustion engine,
Identical elements and elements having the same function are identified in the figures by the same reference numbers.
a and 1b show a fuel injector 1. The latter comprises a seal 6 axially between a lower annular end side 2 of a nozzle clamping nut 3 and a cylinder head 4 of an internal combustion engine 5. The seal 6 protects an upper region 7 of a nozzle body 8, which is clamped against a holding body (not shown) of the fuel injector 1 by the nozzle clamping nut 3, against combustion products from a combustion chamber 9 of the internal combustion engine 5, into which combustion chamber the nozzle body 8 projects axially with a lower nozzle shank 10. In particular, the seal 6 protects a transition region 11 between an axial nozzle shank 10 and a nozzle collar 12 (annular shoulder) of the nozzle body 8 against the abovementioned combustion products, the nozzle clamping nut 3 bearing in the axial direction against said nozzle collar 12 and thus applying force to the nozzle body 8 in the axial direction.
The fuel injector 1 is subjected to a clawing force downward in the axial direction of the plane of the drawing against the cylinder head 4 by means of a claw (not illustrated).
In the exemplary embodiment shown, the seal 6 comprises a metal disk 13 which is designed as a copper disk and onto which an elastomeric, annular sealing compound 14 is vulcanized. The elastomeric sealing compound 14 is supported inward in the radial direction on the nozzle shank 10 by a radial sealing force. At the same time, the elastomeric sealing compound 14 rests directly on the cylinder head 4 by means of an axial sealing lip 15, and therefore not only prevents gas from passing through in the direction of the transition region 11 of the nozzle body 8 but also into the surroundings.
a shows a top view of the seal 6 of the fuel injector 1 from below, i.e. in the viewing direction A indicated. It can be seen that an inner circumference 16 of the metal disk 13 is provided with a toothing 17 in order to ensure optimum retention of the elastomeric sealing compound 14.
It follows from
b shows an alternative variant embodiment of a fuel injector 1. A seal 6 is also provided in this variant embodiment to protect the transition region 11 between a nozzle shank 10 of the nozzle body 8 and the nozzle collar 12 of the nozzle body 8. In contrast to the previously described exemplary embodiment, the seal 6 according to
| Number | Date | Country | Kind |
|---|---|---|---|
| 102009000285.5 | Jan 2009 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2009/065434 | 11/19/2009 | WO | 00 | 7/19/2011 |
