WO2003081022A1

WO2003081022A1 - Fuel injection valve

Info

Publication number: WO2003081022A1
Application number: PCT/DE2003/000040
Authority: WO
Inventors: Detlef Nowak
Original assignee: Robert Bosch Gmbh
Priority date: 2002-03-27
Filing date: 2003-01-09
Publication date: 2003-10-02
Also published as: EP1490593A1; KR20040093188A; JP2005520980A; DE10213857A1

Abstract

The invention relates to a fuel injection valve (1), especially for directly injecting fuel into the combustion chamber of an internal combustion engine. The inventive fuel injection valve comprises a valve needle (3) that is provided, on the injection end thereof, with a valve closing body (4) that interacts with a valve face (6), configured on a valve face body (5), to give a sealing seat and that is guided in a guide (35). A swirl device (36) generates a swirl of the fuel in a swirl chamber (37). In the valve seat body (5) an injection opening (7) is provided. An at least partially elastic sealing device (40) prevents the inflow of fuel through a gap (39) between the guide body (35) and the valve closing body (4) into the swirl chamber (37).

Description

Fuel injector

State of the art

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

From DE 197 36 682 AI a fuel injector is known which has a guide body (referred to there as a guide element 35) for guiding the lower, downstream end of the valve needle. The lower, downstream end of the ^' valve needle is referred to as the valve closing body and, in cooperation with the guide body, serves in particular to seal the

Swirl chamber against the penetration of untwisted fuel

^■ which is located upstream of the guide body.

The sealing effect is achieved through a relatively low guide clearance, low-wear materials and low manufacturing tolerances.

A disadvantage of the fuel injector known from the abovementioned publications is, in particular, that the inflow of non-swirled fuel into the combustion chamber is only inadequately achieved through the gap between the guide body and valve closing body. The inflow of swirled fuel through the gap described is also referred to as a leakage flow. To the To keep leakage flow as low as possible over the entire life of the fuel injector, the gap is kept small by using small manufacturing tolerances. On the one hand, manufacturing tolerances cannot be realized as small as desired, so they have limits, on the other hand they become disproportionately more expensive to manufacture the closer the manufacturing tolerances are to those limits. In addition, the gap widens over the course of its service life due to frictional wear. In order to achieve the longest possible service life and to limit the gap widening during this period, expensive, low-wear materials must be used, which are also usually difficult and therefore costly to machine. Finally, a certain gap width must be maintained due to the extreme temperature range to which the fuel injector is exposed during operation, since otherwise reliable operation cannot be guaranteed due to temperature expansions.

In principle, caused by the so-called dead space volume, a so-called pre-jet emerges from the spray opening at the start of the injection. This pre-jet is largely untwisted and always undesirable, since it does not correspond to the desired geometry of the injected fuel cloud and, in particular with direct fuel injection into the combustion chamber, causes deposits in the area of the spray opening, but at least does not counteract it. The leakage flow significantly hinders the swirl preparation of the fuel and leads to a lengthened and enlarged pre-jet. The leakage flow increases in the course of the service life in such a way that the flow values q ^ _yn ^and -d Q _{stat are} outside the permissible tolerance.

To counteract this, the needle stroke and valve opening times can be selected to be small and the number of swirl channels increased. This results in a slow and undisturbed swirl build-up. These measures result however at the same time to a lower valve dynamic. The increased number of swirl channels increases the design effort and thus the costs. The slower swirl build-up increases the sensitivity to dirt and thus the risk of deposits.

Advantages of the invention

The fuel injector according to the invention with the characterizing features of the main claim has the advantage that the leakage flow of fuel passing through the gap between the guide body and the valve closing member is prevented. At the same time, the sealing device according to the invention makes it possible to dispense with cost-intensive measures for reducing the leakage flow, as are known from the prior art. In particular, cost-intensive, low manufacturing tolerances for producing a minimized gap between the guide body and the valve closing body guided in it can be dispensed with. Furthermore, the materials used for the guide body and the valve closing body can be optimized, in particular with regard to the guide function, since the task of leakage current sealing no longer falls within the scope of these components.

Since there is no leakage current, the swirl formation, especially at the beginning, is improved and the pre-jet is reduced. Since the sealing effect of the sealing device according to the invention is permanent, ie is not subject to wear and tear which causes the leakage flow to increase over the service life, the permissible limit values for the jet angle can be reliably maintained over the entire service life of the fuel injector, as can the required flow values q _dyn ^and d Q _stat without having to resort to measures that are detrimental to the valve dynamics. The risk of deposits on the spray geometry of a fuel injector is increased in spray geometries that protrude directly into the combustion chamber or are in direct contact with it. The swirl formation which develops early in the fuel injection valve according to the invention at the start of injection reduces the risk of deposits forming on the spray geometry.

The invention can be used particularly advantageously for fuel injection valves which have a so-called cardanic valve needle guide, since the problem of leakage flow sealing is particularly critical here. The cardanic valve needle guide has a spherical valve closing body on the spray-side end of the valve needle, which is guided in a guide body. The sealing effect to prevent the leakage flow is achieved here by the interaction of the inner surface of the guide body and the only short immediate area around the ball equator of the valve closing body. Due to the much shorter sealing length of the lower valve needle guide compared to fuel injectors with a cylindrical valve closing body, compliance with limit values is even more difficult to master. In particular, the wear and the dependence of the leakage flow on the wear is increased. Nevertheless, fuel injectors with cardanic valve needle guidance have other advantages. In particular, they can be manufactured much more cost-effectively than designs with a cylindrical valve closing body. The sealing device according to the invention allows cost savings in two respects. On the one hand, the measure itself is less expensive than the measures of the prior art. On the other hand, it allows the use of the inexpensive cardanic valve needle guide. The measures listed in the subclaims allow advantageous further developments of the fuel injector specified in the main claim.

Advantageously, the sealing device can be attached to the valve needle via a flange such that the elastic part of the sealing device influences the closing or opening process of the fuel injector. The movements of the valve needle can in particular be damped, slowed down or accelerated.

The shape of the elastic sealing body encompassed by the sealing device should be adaptable to the structural requirements. For example, a toroidal, elastic sealing body conceivable, which is only in its position, e.g. is held between a flange and the Fuhrungskorper, wherein it is constantly acted upon by a compressive force from the outside. In addition, frictional forces or adhesive connections can hold the elastic sealing body in its position.

It is also advantageous that the elastic sealing body consists of an elastomer, since it is widely used

Temperature ranges maintain their elastic properties.

If the valve needle passes through the flange or the elastic sealing body and the flange and the elastic sealing element are disk-shaped, the forces that occur between these parts can be applied to the flange, elastic sealing body, valve needle and guide body evenly. The sealing arrangement of the elastic sealing body between the flange and the guide body has the particular advantage that it is not necessary to connect the elastic sealing element directly to the valve needle. If the valve needle and the elastic sealing element were connected directly, the shear forces that occur would have an unfavorable effect on the service life of the connection. Further advantages arise, for example, in the case of an L-shaped profile of the flange, which can be produced cost-effectively without cutting and also has a higher strength due to the non-cutting production.

drawing

An embodiment of the invention is shown in simplified form in the drawing and explained in more detail in the following description. Show it:

Figure 1 is a schematic section through an embodiment of a fuel injector designed according to the invention.

Fig. 2 is a schematic partial section of the spray-side end of the embodiment of the fuel injector according to it and

Fig. 3 is an enlarged detail of the section designated III of the schematic partial section shown in Fig. 2 in the region of the valve closing body and guide body.

Description of the embodiment

An exemplary embodiment of a fuel injection valve 1 according to the invention shown in FIG. 1 is in the form of a fuel injection valve 1 for fuel injection systems of mixture-compressing, semi-ignited internal combustion engines. The fuel injector 1 is particularly suitable for the direct injection of fuel into a combustion chamber, not shown, of an internal combustion engine.

The fuel fine injection valve 1 consists of a nozzle body 2, in which a valve needle 3 is arranged. The valve needle 3 is operatively connected to a valve closing body 4, which cooperates with a valve seat surface 6 arranged on a valve seat body 5 to form a sealing seat. In the exemplary embodiment, fuel injector 1 is a fuel injector 1 that opens inward and has a spray opening 7. The nozzle body 2 is sealed by a seal 8 against an outer pole 9 of a solenoid 10. The magnet coil 10 is encapsulated in a coil housing 11 and wound on a coil carrier 12 which bears against an inner pole 13 of the magnet coil 10. The inner pole 13 and the outer pole 9 are separated from one another by a constriction 26 and are connected to one another by a non-ferromagnetic connection component 29. The magnet coil 10 is excited via a line 19 by an electrical current that can be supplied via an electrical plug contact 17. The plug contact 17 is surrounded by a plastic sheath 18, which can be molded onto the inner pole 13.

The valve needle 3 is guided in a valve needle guide 14, which is disc-shaped. A paired adjusting disc 15 is used for stroke adjustment. The armature 20 is located on the other side of the adjusting disc 15. This armature is non-positively connected to the valve needle 3 via a first flange 21, which is connected to the valve needle by a weld seam 22. first flange 21 is connected. A restoring spring 23 is supported on the first flange 21, which in the present design of the fuel injector 1 is preloaded by a sleeve 24. Fuel channels 30a to 30c run in the valve needle guide 14, in the armature 20 and in the nozzle body 2. The fuel is supplied via a central fuel supply 16 and filtered by a filter element 25. The fuel injector 1 is sealed by a seal 28 against a fuel rail, not shown, and by a seal 34 against a cylinder head, not shown. An annular damping element 32, which consists of an elastomer material, is arranged on the spray-side side of the armature 20. It rests on a second flange 31, which is non-positively connected to the valve needle 3 via a weld seam 33.

In the idle state of the fuel injection valve 1, the armature 20 is acted upon by the return spring 23 against its stroke direction in such a way that the valve closing body 4 is held in sealing contact with the valve seat surface 6. When the magnetic coil 10 is excited, it builds up a magnetic field which moves the armature 20 against the spring force of the return spring 23 in the stroke direction, the stroke being predetermined by a working gap 27 which is in the rest position between the inner pole 12 and the armature 20. The armature 20 also takes the first flange 21, which is welded to the valve needle 3, in the lifting direction. The valve closing body 4 connected to the valve needle 3 lifts off from the valve seat surface 6, and the fuel supplied via the swirl device 36 is sprayed through the spray opening 7.

If the coil current is switched off, the armature 20 drops from the inner pole 13 after the magnetic field has been sufficiently reduced by the pressure of the return spring 23, as a result of which the first flange 21, which is connected to the valve needle 3, moves counter to the stroke direction. The valve needle 3 is thereby moved in the same direction, as a result of which the valve closing body 4 rests on the valve seat surface 6 and that. Fuel injector 1 is closed.

Furthermore, a guide body 35, a swirl device 36 and the sealing device 40 according to the invention, consisting of a flange 41 and an elastic sealing body 42, are provided, which are explained in more detail with reference to FIG. 2.

The end of the embodiment of the fuel injector 1 shown in FIG 1 comprises in particular a valve closing body 4, a guiding body 35, a swirl device 36 and the sealing device 40 according to the invention. The swirl device 36 is located upstream of the valve seat surface 6, which is formed on the valve seat body 5. In the exemplary embodiment shown, the swirl device 36 consists of a swirl disk 38, the fuel channels (not shown) of which have a tangential component and open into a swirl chamber 37. The fuel is conducted through the fuel channel 30c, past the flange 41, the elastic sealing body 42 and the guide body 35 to the swirl disk 38. After the fuel has passed the swirl disk 38, it enters the dali chamber 37 with a directional component that is tangential to the valve needle axis 43, is swirled and finally sprayed through the spray opening 7 into the combustion chamber (not shown).

The sealing device 40 according to the invention, which in this exemplary embodiment consists of the flange 41 and the elastic sealing body 42, prevents the entry of fuel from the fuel channel 30c through the gap 39 between the guide body 35 and the valve closing element 4 in FIG the swirl chamber 37. The flange 41 is hydraulically sealed and non-positive, for example attached to the valve needle 3 by welding, soldering, gluing, pressing and / or shrinking. The elastic sealing body 42 is always in hydraulic contact with the flange 41 as well as with the upstream side of the guide body 35. For this purpose, the dimensions and the elasticity of the elastic sealing body 42 are dimensioned such that the sealing body 42 holds a hydraulically sealing connection between the guide body 35 and the flange 41 both when the fuel injector 1 is closed and when it is open.

All parts of the sealing device 40 and their connection points are temperature resistant and corrosion-resistant and further constructed and attached so that they do not significantly increase the force required to close the fuel injector 1 and thus do not significantly affect the valve dynamics. The selection of materials and the shape of the parts of the sealing device 42 are optimized, inter alia, for low weight in order to keep inertial forces low. The Fuhrungskorper 35 is used to guide the downstream part of the valve needle 3 over the spherical valve closing body 4. The arrangement shown with spherical valve closing body 4, which takes over the downstream guidance of the valve needle 3 through the guide body 35, is also referred to as a cardan valve needle guide.

Fig. 3 shows a detail enlargement of the greatly exaggerated gap 39, which arises between the spherical valve closing body 4 and the guide body 35 through play. The elastic sealing body 42 is attached upstream of the guide body 35.

The invention is not limited to the illustrated embodiments and z. B. also applicable for outward opening fuel injectors.

Claims

Expectations

1. Fuel injection valve (1), in particular for the direct injection of fuel into a combustion chamber of an internal combustion engine, with a valve needle (3) which has a valve closing body (4) on an injection-side end, which has a valve seat surface (6) on a valve seat body (5), cooperates to form a sealing seat, and is guided in a guide body (35), a swirl device (36) for generating a swirl of the fuel in a swirl chamber (37) and a spray opening (7) provided downstream of the valve seat surface (6) ), characterized in that an at least partially elastic sealing device (40) prevents the inflow of fuel through a gap (39) between the guide body (35) and valve closing body (4) into the swirl chamber (37).

2. Fuel injection valve according to claim 1, characterized in that the sealing device (40) comprises an elastic sealing body (42) which exerts tensile or compressive forces indirectly or directly on the valve needle (3) along the directions of movement of the valve needle (3).

3. Fuel injection valve according to claim 2, characterized in that the elastic sealing body (42) has a toroidal shape or

Has hollow cylindrical shape.

4. Fuel injection valve according to claim 2, characterized in that the elastic sealing body (42) is disc-shaped.

5. Fuel injection valve according to one of claims 2 to 4, characterized in that the elastic sealing body (42) is penetrated by the valve needle (3).

6. Fuel injection valve according to one of claims 2 to

5, characterized in that a flange (41) is firmly connected to the valve needle (3) and the elastic sealing body (42) is clamped between the flange (41) and the guide body (35).

7. Fuel injection valve according to claim 6, characterized in that the flange (41) is penetrated by the valve needle (3).

8. Fuel injection valve according to claim 6 or 7, characterized in that the flange (41) has an L-shaped cross-sectional profile.

9. Fuel injection valve according to one of claims 6 to 8, characterized in that the flange (41) is non-positively attached by a joining process to the valve needle (3), in particular by welding, soldering, gluing, pressing and / or shrinking.

10. Fuel injection valve according to one of claims 2 to 9, characterized in that the elastic sealing body (42) consists of an elastomer.

11. Fuel injection valve according to one of claims 2 to 10, characterized in that the elastic sealing body (42) is held in position by external friction.

12. Fuel injection valve according to one of claims 2 to 10, characterized in that the elastic sealing body (42) is held in its position by positive locking.

13. Fuel injection valve according to one of claims 2 to 10, characterized in that the elastic sealing body (42) by a

Adhesive connection is held in position.