WO2001002719A1

WO2001002719A1 - Fuel-injection valve

Info

Publication number: WO2001002719A1
Application number: PCT/DE2000/002043
Authority: WO
Inventors: Hans Lander; Petra Heinbuch; Frank Schatz; Armin Glock; Ulrich Schulmeister; Guido Pilgram; Thomas Hofmann; Ullrich Kraatz; Guenter Dantes; Detlef Nowak; Joerg Heyse; Juergen Hackenberg
Original assignee: Robert Bosch Gmbh
Priority date: 1999-07-02
Filing date: 2000-06-30
Publication date: 2001-01-11
Also published as: EP1198670A1; DE50012054D1; EP1198670B1; JP2003503637A; CN1171013C; CN1359448A

Abstract

The invention relates to a fuel-injection valve (5), in particular, a fuel-injection valve which projects directly into the combustion chamber of an internal combustion engine, comprising a fuel inlet (7), an excitable actuating element (10, 11, 19) which can displace a valve closing element (28), a fixed valve seat (27) which interacts with the valve closing member (28) to open and close the valve and comprising a fuel outlet which is configured in a valve end (8) that is located downstream. The fuel outlet is formed from at least one exit opening (32) which is located downstream of the valve seat (27). The valve-seat element (26) which has at least one exit opening (32) has a coating at least in the mouth area (55) of the exit opening (32) on its downstream face (54) which prevents coke deposits in this area.

Description

Fuel injector

State of the art

The invention relates to a fuel injector according to the preamble of the main claim.

During engine operation, the problem generally arises in the direct injection of a fuel into the combustion chamber of an internal combustion engine, in particular in the case of direct petrol injection or the injection of diesel fuel, that the downstream tip of the injection valve protruding into the combustion chamber cokes or deposits due to fuel deposits Accumulate soot particles formed on the flame front at the valve tip. In the case of previously known injection valves projecting into the combustion chamber, there is therefore a risk of a negative influence on the spray parameters (e.g. static flow quantity, jet angle, droplet size, stringiness) over their service life, which can lead to malfunctions of the internal combustion engine or to failure of the injection valve.

Advantages of the invention

The fuel injector according to the invention with the characterizing features of the main claim has the Advantage that these aforementioned negative effects of coking (soot deposition) on the valve tip protruding into the combustion chamber are restricted or eliminated. By applying coatings to the downstream valve end according to the invention, above all around the mouth areas of the outlet openings, the coking or deposit formation (soot) at the valve end, which generally negatively influences the spray parameters and the valve function, is reduced or prevented.

The measures listed in the subclaims allow advantageous developments and improvements of the fuel injector specified in the main claim.

It is advantageous to apply layers at the valve end through which either a catalytic conversion (combustion) of the deposits takes place or the surface energy and / or the surface roughness of the component to be coated is reduced, as a result of which

Change in wetting behavior is achieved, or the formation of a reaction layer is prevented.

drawing

An embodiment of the invention is shown in simplified form in the drawing and explained in more detail in the following description. FIG. 1 shows a fuel injector inserted into a receiving bore of a cylinder head, FIG. 2 shows a fuel injector

3 shows a first exemplary embodiment of a valve end coated according to the invention, FIG. 4 shows a second exemplary embodiment of a valve end coated according to the invention, FIG. 5 shows an alternative guide and 6 shows a longitudinal section of a fuel injection valve for self-igniting internal combustion engines and FIG. 7 shows the end of the fuel injection valve on the combustion chamber side according to FIG. 6.

Description of the embodiments

In FIG. 1, a cylinder head 1 of an internal combustion engine, in particular a mixture-compressing spark-ignition internal combustion engine, is shown cut out in a detail. A stepped receiving bore 2 is formed in the cylinder head 1 and extends symmetrically up to a combustion chamber 3 along a longitudinal axis 4. A fuel injection valve 5 according to the invention is inserted into the receiving bore 2 of the cylinder head 1. The fuel injection valve 5 is used for the direct injection of fuel, in particular gasoline, but also e.g. Diesel, as shown in FIGS. 6 and 7, into the combustion chamber 3 of the internal combustion engine.

The fuel injector 5 can preferably be actuated electromagnetically via an electrical connecting cable 6. The fuel is fed to the fuel injection valve 5 via an inlet connection 7. The fuel injector 5 shown in FIG. 1 is a so-called top-feed injector, in which the fuel is directed from the inlet nozzle 7 through the entire injector 5 in the axial direction, at the injection-side end 8 opposite the inlet end the combustion chamber 3 is hosed down.

In order to protect the fuel injection valve 5 near the combustion chamber 3 against overheating, the injection valve 5 is, for example, also in the receiving bore 2 introduced heat protection sleeve 9 at least partially surrounded, but which can also be dispensed with.

FIG. 2 shows an exemplary embodiment of a fuel injection valve 5 according to the invention in a sectional illustration. This is an electromagnetically actuated valve which has a tubular, largely hollow cylindrical core 11, which is at least partially surrounded by a magnetic coil 10 and serves as the inner pole of a magnetic circuit. For example, a stepped coil body 13 made of plastic takes up the winding of the magnetic coil 10 and, in conjunction with the core 11 and a non-magnetic intermediate part 14, which is partially surrounded by the magnetic coil 1, enables a particularly compact and short structure of the injection valve in the area of the magnetic coil 1 Electromagnetic actuator, the fuel injector 5 can also be actuated piezoelectrically or magnetostrictively.

A continuous longitudinal opening 15 is provided in the core 11, which extends along a longitudinal valve axis, which coincides with the longitudinal axis 4 of the receiving bore 2. The core 11 of the magnetic circuit also serves as an inlet connection 7. An outer metallic (for example ferritic) housing part 16, which closes the magnetic circuit as the outer pole or outer guide element and the magnetic coil 1 at least, is firmly connected to the core 11 above the magnetic coil 1 completely surrounds in the circumferential direction. In the longitudinal opening 15 of the core 11, a fuel filter 17 is provided on the inlet side, which ensures that those fuel components are filtered out which, because of their size, could cause blockages or damage in the injection valve. At the upper housing part 16, a lower tubular housing part 18 connects tightly and firmly, which, for. B. an axially movable valve part consisting of an armature 19 and a rod-shaped valve needle 20 or an elongated valve seat support 21 encloses or receives. The two housing parts 16 and 18 are, for. B. firmly connected to each other with a circumferential weld. The seal between the housing part 18 and the valve seat support 21 takes place, for. B. by means of a sealing ring 22. The valve seat support 21 has over its entire axial extent an inner through opening 24 which is concentric with the longitudinal axis of the valve.

With its lower end, which also represents the downstream termination of the entire fuel injection valve 5, the valve seat support 21 surrounds a disk-shaped valve seat element 26 fitted in the through opening 24 with a frustoconical tapering shape downstream

Valve seat surface 27. In the through opening 24, the valve needle 20 is arranged, which has a valve closing section 28 at its downstream end. This, for example spherical, partially spherical or tapered valve closing section 28 interacts in a known manner with the valve seat surface 27 provided in the valve seat element 26. Downstream of the valve seat surface 27, at least one outlet opening 32 for the fuel is introduced in the valve seat element 26.

Serves to guide the valve needle 20 during its axial movement with the armature 19 along the longitudinal axis of the valve on the one hand, a guide opening 34 provided in the valve seat support 21 at the end facing the armature 19 and, on the other hand, a disk-shaped guide element 35 arranged upstream of the valve seat element 26 with a dimensionally accurate guide opening 36.

The stroke of the valve needle 20 is predetermined by the installation position of the valve seat element 26. An end position of the valve needle 20 is when the solenoid 1 is not excited by the contact of the valve closing section 28 on the

Valve seat surface 27 of the valve seat element 26 is fixed, while the other end position of the valve needle 20 results when the magnet coil 1 is excited due to the contact of the armature 19 on the downstream end face of the core 11. The surfaces of the components in the latter stop area are chromed, for example.

The electrical contacting of the magnetic coil 1 and thus its excitation takes place via contact elements 43 which are outside the coil body 13 with a

Plastic extrusion 44 are provided. The plastic encapsulation 44 can also extend over further components (eg housing parts 16 and 18) of the fuel injection valve 5. The electrical runs out of the plastic extrusion 44

Connection cable 6, via which the energization of the magnet coil 1 takes place.

The guide and provided in the spray-side end of the valve seat support 21 in its through opening 24

The seating area is formed by three axially consecutive, disc-shaped, functionally separate elements. In Downstream direction are successively followed by the guide element 35, a swirl element 47 and the valve seat element 26. A compression spring 50 enveloping the valve needle 20 braces the three elements 35, 47 and 26 in the valve seat carrier 21. The swirl element 47 can be inexpensively, for example, by means of punching, wire EDM, laser cutting, etching or other known methods from a sheet or by electrodeposition. An inner swirl chamber and a plurality of swirl channels opening into the swirl chamber are provided in the swirl element 47. In this way, a swirl component is impressed on the fuel to be sprayed off in front of the valve seat 27, so that the flow enters the outlet opening 32 with swirl and a finely swirled and well atomized spray is released into the combustion chamber 3.

In engine operation, the problem generally arises with the direct injection of a fuel into the combustion chamber of an internal combustion engine, that in the

The combustion chamber protruding downstream tip of the injection valve carbonized by fuel deposits or soot particles formed in the flame front accumulate on the valve tip. In the case of previously known injection valves protruding into the combustion chamber, there is therefore a risk of a negative influence on the spray parameters (e.g. static flow rate, spray angle, droplet size, stringiness) over their service life, which can lead to malfunctions of the internal combustion engine or to failure of the injection valve.

According to the invention, the aforementioned problems are restricted or eliminated by applying coatings to the valve end 8. Different coatings have different effects on the surface 54 of the component to be coated, for example on the valve seat element 26 made of Cr steel, but ultimately all measures are aimed at coking or deposit formation (soot) which generally negatively influences the spray parameters and the valve function

To reduce or prevent valve end 8. Individual coating options are described in more detail below.

The catalytically active layers represent a first group of coatings. The electrolytically applied layers ensure a catalytic conversion (combustion) of the deposited soot particles or prevent the deposition of carbon particles from the outset. Suitable materials for such a coating

Avoiding coking are cobalt and nickel oxides and oxides of alloys of the metals mentioned. The noble metals Ru, Rh, Pd, Os, Ir and Pt or alloys of these metals with one another or with other metals also show catalytic activity. The desired layers are e.g. generated by electrochemical or electroless metal deposition. In the case of Ni, Co or their alloys, the formation of oxide in air or an additional oxidation step (wet chemical, plasma) can also be used.

The coatings with which the wetting behavior on the corresponding surface 54 is changed form a second large group. It is achieved by the coatings that the surface energy and / or the surface roughness of the critical areas at the valve end 8 is reduced. The interfacial energy between surface 54 and the fuel is thereby increased, causing wetting to deteriorate. In this way, the fuel droplets can roll off at the areas coated according to the invention and from the surrounding areas Flow at the valve end 8 are carried away. Permanent wetting of the valve end 8 no longer takes place. Such layers are ceramic layers, carbon layers, which can be metal-containing or metal-free, or fluorine-containing layers. The fluorine-containing layers are, for example, thermoresistant PTFE-like layers or in particular organic ceramic layers or so-called Ormocer® layers made of fluorosilicate (FAS). Such fluorine-containing layers are applied, for example, by spraying or dipping. Sapphire layers are also conceivable.

A third group consists of the coatings with which a reaction layer can be prevented. These include e.g. Nitrite layers (TiN, CrN) or oxide layers (tantalum oxide,

Titanium oxide). Similar to sputtering, in these layers, evaporated particles are deposited in a vacuum oven on the surfaces 54 to be coated.

At the valve end 8, in particular the areas are to be coated which directly surround the at least one outlet opening 32 in its mouth area 55. An accumulation of soot particles in the outlet opening 32 or at its immediate boundary edge leads in particular to the above-mentioned adverse influence on the spray parameters (e.g. static flow rate, jet angle, droplet size, stringiness). A coating should therefore in any case be carried out at the downstream end (mouth region 55) of each individual outlet opening 32, regardless of the component of the fuel injection valve 5 on which the outlet openings 32 are formed.

FIGS. 3 and 4 show two exemplary embodiments of valve ends 8 coated according to the invention Shown subviews, which differ in that once the entire downstream component surface 54 of the component having the outlet opening 32, here the valve seat element 26, is coated (FIG. 3) and in the other case only an annular partial area of the downstream component surface 54 around the at least one Outlet opening 32 is coated (Figure 4). The dotted areas are intended to illustrate the coated areas. The mouth regions 55 of the outlet openings 32 lie in FIGS. 3 and 4 in FIG

Plane. It should be emphasized that the coatings can also extend slightly into the outlet opening 32.

In the illustrated exemplary embodiments, the valve seat element 26 is the component of the

Fuel injection valve 5, which forms the downstream end 8 and has the outlet opening 32, so that the coating is to be carried out on the downstream end face 54 of the valve seat element 26. However, the application of a coating according to the invention is not limited to a valve seat element; rather, other valve components, which form the downstream valve end 5 and thus protrude into the combustion chamber 3, can also have such a coating. Even for those downstream of the

Components seat valve 27 arranged (see spray body 67 in Figure 5) applies that at least the areas are to be coated directly at the outlet openings 32, so that the actual spray area is protected against coking.

FIG. 5 shows an alternative guiding and seating area at the spray-side valve end 8 in order to make it clear that the statements regarding the coating according to the invention also apply to valve designs that differ from the design. at In this exemplary embodiment, a further disk-shaped spray body 67 is arranged downstream of the valve seat element 26. In this case, the spray body 67 has the outlet opening 32. The outlet opening 32 is introduced at an incline to the longitudinal axis of the valve, it ending downstream in a convexly curved spray region 66. The spray body 67 and the valve seat element 26 are, for example, firmly connected to one another via a weld seam 68 achieved by means of laser welding, the welding being carried out in an annular circumferential recess 69. The spray body 67 is also fixedly connected to the valve seat support 21 by a weld 61. The coating takes place, for example, either over the entire curved spray area 66 or directly in a ring around the

Mouth area 55 of the outlet opening 32 so that there is an off-center coating on a curved surface 54 with respect to the longitudinal valve axis.

In Figure 6 is a longitudinal section through a

Fuel injection valve for self-igniting internal combustion engines, in particular diesel engines, shown, only the part facing the combustion chamber being shown. An increase in the end of the fuel injection valve 5 shown in FIG. 6 on the combustion chamber side is shown in FIG. A component designed as a valve body 72 is clamped with a clamping nut 75 against a valve holding body 73. A bore 84 is formed in the valve body 72, in which the piston-shaped valve needle 20, which is axially movable against a closing force, is arranged. The bore 84 is designed as a blind bore, the closed end facing the combustion chamber 3 forming a valve seat surface 27 which is essentially frustoconical. By bulging the end of the valve seat on the combustion chamber side 27, a blind hole 92 is formed, in the wall of which at least one outlet opening 90 connecting the blind hole 92 to the combustion chamber 3 is arranged.

The valve needle 20 is subdivided into a larger-diameter section facing away from the combustion chamber 3, which is guided in the bore 84, and a smaller-diameter section between which and the wall of the bore 84 a pressure chamber 86 is formed, which via a Valve holder body 73 and inlet channel 80 formed in valve body 72 can be filled with fuel under high pressure. Due to the gradation of the outer diameter of the valve needle 20, a pressure shoulder 82 is formed thereon, which is arranged within the pressure chamber 86. The fuel pressure in the pressure chamber 86 generates a force on the pressure shoulder 82, the component acting in the axial direction of which is opposite to the closing force acting on the valve needle 20 and can thus move the valve needle 20 against the closing force given a corresponding fuel pressure.

At the end of the combustion chamber on the valve needle 20, a valve sealing surface 88 forming the valve closing section 28 is formed, which cooperates with the valve seat surface 27 in such a way that the at least one outlet opening 90 is sealed against the pressure chamber 86 by the valve sealing surface 88 resting on the valve seat surface -27. Due to the inward opening stroke movement directed away from the combustion chamber 3, the valve sealing surface 88 lifts off the valve seat surface 27 and connects the pressure chamber 86 to the outlet opening 90.

The catalytically active coating takes place, for example, over the entire end face of the valve body 72 facing the combustion chamber 3. It can also be provided that only the curved outer surface 96 of the blind hole wall 93 which defines the blind hole 92 and in which the at least one outlet opening 90 is formed, is provided with a coating. It can further be provided that the coating continues into the outlet opening 90.

Claims

Expectations

1. Fuel injection valve (5), in particular directly into a combustion chamber (3) of an internal combustion engine, fuel injector (5), with a fuel inlet (7), with a movable valve closing member (28), with a fixed valve seat (27) with which the valve closing member (28) for opening and closing the valve, and having a fuel outlet formed in a downstream valve end (8), the fuel outlet being formed by at least one outlet opening (32, 90) arranged downstream of the valve seat (27), characterized in that the component (26, 67, 72) having the at least one outlet opening (32, 90) has a coating at least in the mouth region (55) of the outlet opening (32, 90).

2. Fuel injection valve according to claim 1, characterized in that the fuel injection valve projects into the combustion chamber (3) of a spark ignition internal combustion engine.

3. Fuel injection valve according to claim 1, characterized in that the fuel injection valve projects into the combustion chamber (3) of a self-igniting internal combustion engine.

4. Fuel injection valve according to one of the preceding claims, characterized in that the coating is provided annularly around the outlet opening (32, 90) of the downstream surface (54, 96) of the component (26, 67, 72).

5. Fuel injection valve according to one of claims 1 to 3, characterized in that the coating is provided over the entire area on the downstream surface (54, 96) of the component (26, 67, 72).

6. Fuel injection valve according to one of claims 4 or

5, characterized in that the coating also extends into the outlet opening (32, 90) in addition to the coating of the surface (54, 96) of the component (26, 67, 72).

7. Fuel injection valve according to one of claims 1 to

6, characterized in that the coating in the form of a catalytically active layer of Co or Ni or

Cobalt or nickel oxides or oxides of Co or Ni alloys or Ru or Rh or Pd or Os or Ir or Pt or alloys of these metals with one another or with other metals.

8. Fuel injection valve according to claim 7, characterized in ^" that the layer can be generated by electrochemical or electroless metal deposition.

9. Fuel injection valve according to one of claims 1 to 6, characterized in that the coating is carried out as a metal-containing or metal-free carbon layer.

10. Fuel injection valve according to one of claims 1 to 6, characterized in that the coating is carried out as a fluorine-containing layer.

11. The fuel injector according to claim 10, characterized in that the fluorine-containing layer is a layer made of fluorosilicate (FAS).

12. Fuel injection valve according to one of claims 1 to 6, characterized in that the coating as

Nitrite layer (TiN, CrN) is made.

13. Fuel injection valve according to one of claims 1 to 6, characterized in that the coating is carried out as a tantalum oxide layer or titanium oxide layer.

14. Fuel injection valve according to one of the preceding claims, characterized in that the component which has at least one outlet opening (32, 90) is also a valve seat element (26, 72) which has the valve seat (27).

15. The fuel injector according to claim 14, characterized in that the valve seat element (26) has an upstream end face, on which the valve seat face (27) is formed, and has a downstream end face (54) opposite the upstream end face, to which the coating is applied is.