Intermediate element for a fuel injector

An intermediate element for a fuel injector situated in a cylinder head of an internal combustion engine is disposed between a valve housing of the fuel injector and a wall of a receiving bore of the cylinder head, and/or between the valve housing and a clamping shoe holding the fuel injector down in the cylinder head. The intermediate element is made up of a plurality of layers having different patterning and/or being made of different materials.

RELATED ART

The present invention is based on an intermediate element for a fuel injector.

From DE 101 08 466 A1, for instance, an intermediate element for supporting a fuel injector in a cylinder head of an internal combustion engine is known. The intermediate element is in the form of an annular washer and situated between a valve housing of the fuel injector and a wall of a receiving bore of the cylinder head. The annular washer has a round or oval cross section, and a shoulder of the valve housing is set apart from a shoulder of the cylinder head by the annular washer.

A particular disadvantage of known annular washers is that, although the positioning of the fuel injector in the cylinder head is able to be corrected, the solid design of the annular washer made of wire, copper, steel or similar materials creates a structure-borne noise bridge between the fuel injector and the cylinder head. This transmits the structure-borne noise, which is generated in the fuel injector by the switching pulses, to other components of the internal combustion engine and generates annoying noise.

SUMMARY OF THE INVENTION

In contrast, the intermediate element for a fuel injector according to the present invention, has the advantage that a suitable design of an intermediate element between the fuel injector and the cylinder head and/or between the fuel injector and a pinning-down clamping shoe, or a spring element, effects a decoupling of the fuel injector, which reduces the transmission of structure-borne noise to other components of the internal combustion engine. The intermediate element has a plurality of layers, i.e., at least three layers, which have different forms and/or are made of different materials.

The measures specified in the dependent claims make possible advantageous further refinements and improvements of the intermediate element indicated in the main claim.

In particular, it is advantageous that the number of intermediate layers is variable and adaptable to the given situation.

In an advantageous manner, the layers are provided with patterning, which may take the form of a corrugated sheet, wafer or honeycomb.

The patterns of adjacent layers may be arranged in an in-phase manner, in phase opposition or rotated with respect to each other in order to allow only point-wise contact of adjacent layers so as to dampen the structure-borne noise in this manner.

The layers may be implemented by different methods during the manufacturing process, by soldering, welding, crimping, clamping or compressing, for instance. A cup-shaped design of the bottom layer facilitates the connection.

The interconnection of the layers may be implemented both only radially on the outside as well as radially on the outside and on the inside.

The cavities between the intermediate layers may be provided with suitable fillers such as metal shavings or balls of materials such as metal, plastic, or mineral balls in order to dampen the structure-borne noise even further.

Moreover, it is advantageous that the layers alternately may be made of metal and plastics and/or materials containing carbon fiber.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1shows a schematized part-sectional view through an exemplary embodiment of a fuel injector1equipped with an intermediate element8according to the present invention, in a receiving bore of a cylinder head of a mixture-compressing internal combustion engine having externally supplied ignition.

Here, a fuel injector1is designed as a directly injecting fuel injector1and installed in a cylinder head2of an internal combustion engine. At an end3on the intake side, fuel injector1is provided with a plug connection to a fuel-distributor line4, which is sealed by a seal5between fuel-distributor line4and a supply connection6of fuel injector1. Fuel injector1has an electrical connection7for the electrical contacting in order to actuate fuel injector1.

According to the present invention, fuel injector1has an intermediate element8in receiving bore9of cylinder head2, between a wall11of receiving bore9and a valve housing10of fuel injector1, and/or between valve housing10and a clamping shoe14on the side of the cylinder head, or a spring element, by which fuel injector1is held down in cylinder head2of the internal combustion engine, the intermediate element serving the purpose of decoupling the structure-borne noise and simultaneously regulating the position of fuel injector1.

Intermediate element8thus fulfills several functions. On the one hand, the introduction of structure-borne noise of fuel injector1into cylinder head2and into additional components of the internal combustion engine is reduced. This is desirable since fuel injectors1, in particular piezoelectrically actuated fuel injectors1, generate very high structure-borne noise excitations at the installation location in cylinder head2due to the high switching forces and the short trigger pulses. Furthermore, given the multiple injections that are prevalent today, the structure-borne noise is amplified further by the increased number of injection pulses.

Moreover, by setting fuel injector1apart from a wall11of receiving bore9, centering of fuel injector1is able to be achieved, which counteracts tilting of fuel injector1, for example in the region of a nozzle body12of fuel injector1, and thereby contributes to the sealing action of a sealing ring13, which is slipped onto nozzle body11and seals cylinder head2from the combustion chamber (not shown further) of the internal combustion engine.

In addition, without requiring expensive reworking of the components, intermediate element8is able to compensate for manufacturing tolerances of the individual components, such as nozzle body12or valve housing10, which lead to asymmetries in fuel injector1.

Intermediate element8may also compensate for temperature-related tolerances that may occur as a result of warming of fuel injector1and of cylinder head2during operation of the internal combustion engine. For instance, tolerances of this type may lead to stressing and warping of the plug connection between fuel injector1and fuel distributor line4.

In the following text, exemplary embodiments for intermediate elements8configured according to the present invention and schematically shown in the figures of the drawing will be elucidated in greater detail.

FIGS. 2A through 2Cshow heavily schematized exemplary embodiments for intermediate elements8configured according to the present invention, in a sectional side view.

According to the present invention, intermediate elements8are made up of a plurality of layers15such as three to five, which may have different forms and/or may be made of different materials. Layers15are made from sheet metal, for instance, having a material strength of approx. 0.1 to 0.5 mm or less. At least one of layers15has patterning that prevents an all-over contact at abutting layers15and thereby prevents the transmission of structure-borne noise.

The exemplary embodiments according toFIG. 2A through 2Ceach have a bottom layer15a, a cover layer15b, as well as a plurality of intermediate layers15, of which there are three in the exemplary embodiment. Intermediate layers15cmust be made of non-degradable materials and materials that are dimensionally stable over the service life of fuel injector1.

Intermediate layers15cin the exemplary embodiments shown have patterning in a corrugated-sheet or wafer form, which is able to be produced by, for instance, stamping or deep-drawing with material strengths of tenths, hundredths or thousands of millimeters. The patterning may be arranged in phase-opposition (FIG. 2A) or in phase (FIG. 2B) with respect to each other. Intermediate layers15cmay also have a trapezoidal cross-section (FIG. 2C), and the trapezoidal patterning may likewise be arranged in phase or in phase opposition. Due to the fact that individual layers15of intermediate element8do not make contact allover, but only along lines, effective damping of the structure-borne noise is able to be achieved.

A further improvement in the decoupling may be realized if intermediate layers15cprovided with the patterning are rotated with respect to each other, at an angle of approximately 90°, for instance, as illustrated inFIG. 3Ain a heavily schematized manner. This reduces the contact surfaces to individual points, which causes even less structure-borne noise to be transmitted.

A similarly effective result is shown in the exemplary embodiment according toFIG. 3Cin which a honeycomb-like pattern for intermediate layer15c, of which there is only one, is provided.

Layers15of intermediate element8may be interconnected in a variety of ways in order to prevent displacement of layers15with respect to each other. Methods such as, in particular, beading, crimping, welding or soldering may be considered.

FIGS. 4A and 4Bshow one possible type of connection using a projecting, form-fitting collar16, which is integrally formed with bottom layer15ain the shape of a cup. Collar16, as illustrated inFIG. 4A, may be formed only radially on the outside in order to prevent sliding of layers15in this manner. Intermediate element8then remains open radially toward the inside and has a certain susceptibility with respect to transverse forces. This may be countered by affixing collar16radially on the inside as well, as can be gathered fromFIG. 4B.

The introduction of force into intermediate element8must be implemented only to bottom or cover layer15a,15b, respectively, since a rigid design of cup-shaped bottom layer15awould in turn form a bridge for structure-borne noise. Therefore, it must be ensured that clamping shoe14abuts only against cover layer15b, or that the diameter of intermediate element8in the installation position in cylinder head2is adapted to the diameter of valve housing10, so that a force introduction via bottom or cover layer15a,15b, respectively, and not via collar16, takes place here as well.

Another type of connection is beading, which is illustrated inFIGS. 5A and 5Bin the same representation as inFIGS. 4A and 4B. Collar16is formed by cover layer15band beaded with cup-shaped bottom layer15a. This may likewise be implemented only radially outside or radially outside and inside.

FIGS. 6A and 6Bshow additional types of connection of bottom and cover layers15a,15b, respectively, as well as an additional advantageous embodiment of intermediate layers15cfor damping the structure-borne noise.

The connection between layers15may also be implemented with the aid of welding or soldering, by welding or soldering cover layer15bto bottom layer15a, which is again drawn upward in the shape of a cup. It is no longer necessary to form a collar16, which is why this form of connection is able to be especially easy to produce.

Furthermore, as can be gathered fromFIGS. 6A and 6B, cavities17situated between intermediate layers15cmay be filled with suitable filler material18such as metal shavings, metal balls or plastic balls in order to further dampen the transmission of structure-borne noise.

Another possibility for assembling layers15in packets is schematically illustrated inFIG. 7, where the connection is implemented mechanically, by clamps19that enclose layers15.

Finally, it is also conceivable to set layers15during the production process of intermediate element8, using a force that is considerably higher than the operating force, by a factor of 1.2 to 2, for example. Layers15may be interconnected in this manner as well.

In order to further simplify the production of intermediate element8, it is likewise conceivable to dispense with intermediate layers15cprovided with patterning and instead replace them by intermediate layers15cmade of plastic, or by intermediate layers15creinforced by carbon fiber. The materials used in this connection must be temperature-stable up to approx. 150° C., and relaxation-free.

The present invention is not limited to the exemplary embodiments shown and, for example, is also applicable to fuel injectors1for injection into the combustion chamber of a self-igniting internal combustion engine. All features of the present invention may be combined with one another as desired.