EP1328724A2

EP1328724A2 - Fuel injection valve

Info

Publication number: EP1328724A2
Application number: EP01987847A
Authority: EP
Inventors: Norbert Keim
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2000-10-20
Filing date: 2001-10-19
Publication date: 2003-07-23
Also published as: WO2002033248A2; WO2002033248A3; DE10052146A1; JP2004511720A

Abstract

A fuel injection valve (1), opening to the interior, with a stroke limitation, for fuel injection units in internal combustion engines, comprises a valve closing body (4), in working connection with a valve needle (3) and co-operating with a valve seating surface (6) on a valve seating body (5) to give a sealing seat. Downstream of the sealing seat an projection (34) is arranged on the valve closing body (4), comprising a sleeve-like section (36), extending through a through opening (37) in the valve seating body (5). The projection (34) comprises a radial extension (35) on the downstream end thereof, which has an axial separation from a locating face (32) in the valve seat body (5) and which is larger than the smallest radial extent of the through opening (37).

Description

Brexmstoffeinspritzventil

State of the art

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

Inward opening fuel injection valves with swirl generation are known for example from DE 198 15 800 AI. A ^'tzkörper in a Ventilsi befindliches component of the formed by valve closing body and the valve seat body sealing seat is generated downstream in the fuel flow open, fuel injection valve, a swirl, which results in a fanning out of the ejected fuel jet. The fuel already flows through a swirl disk during the opening process, so that a swirl is formed during the entire injection process. A ^" peripheral speed ^{" is applied to} the fuel immediately when the fuel is sprayed off.

Another inward opening fuel injection valve with a swirl generation downstream of the valve sealing seat is known from DE 41 31 499 Cl. Recesses are arranged downstream of the sealing seat in the valve seat body and have a tangential component and in open a spray opening. The recesses are made in the form of grooves in the valve seat body and run in the conical, downstream extension of the valve sealing seat. When the fuel injection valve is open, these are open towards the valve closing body and part of the fuel flow can flow past the swirl-forming elements to the spray opening. Only part of the fuel to be injected thus contributes to the formation of a swirl, as a result of which the possibilities for influencing the spray geometry of the fuel are restricted.

Both fuel injectors move the valve needle and the valve closing body connected to it between two stroke-limiting stops. When the solenoid coil is not energized, the valve seat surface forms the downstream stroke limitation in the idle state of the fuel injector. When the fuel injection valve is open, the valve needle, together with the valve closing body, is lifted from the valve seat surface until the movement of the armature is limited on an upstream contact surface.

With the fuel injectors mentioned, it is necessary to protect both the stroke-limiting upper stop and the stroke-limiting lower stop from wear. This happens through e.g. Hardening or chrome plating. The treatment of at least four involved components is time and cost intensive.

Furthermore, to set the stroke, the gap between the armature and the associated contact surface must be observed exactly. Starting from the valve seat of the fuel injector in idle state, the component tolerances add up to the armature. Added to this are the component tolerances summed up from the opposite side of the valve up to the contact surface. Advantages of the invention

The fuel injector according to the invention with the characterizing features of the main claim has the advantage that the stroke limitation of the valve closing body for both end positions is realized in one component. Both contact surfaces serve as counter bearings for the valve closing body and are arranged in the valve seat body. The stroke setting can therefore be determined solely by the length of an extension on the valve closing body, which determines the limitation of the stroke when the solenoid coil is energized. The extension is mounted when the valve closing body is in contact with the valve seat surface. This makes it very easy to check the set stroke.

Advantageous developments of the fuel injector according to the invention are possible through the measures listed in the subclaims.

, Two flow paths are formed when the fuel injector is opened. For one thing, the fuel is already flowing. through the fuel channels into the central spray opening of the extension. In addition, some of the fuel flows outside the extension without causing swirl formation. This can be used to generate a pre-jet ^■ which deviates from the main beam of his Abspritzbildes fully open fuel injector terms. Fuel injection valves that are able to implement a partial stroke can also specifically change the geometry of the injected fuel jet during the entire injection process by enabling the second flow path. Furthermore, the dead volume is very low. After the fuel injector is closed, there is no dripping. A swirl is formed immediately before the fuel is sprayed off. The lack of flow diversion leads to a reduction in the sample spread.

drawing

Embodiments of the invention are shown in simplified form in the drawing and explained in more detail in the following description. Show it:

Fig. 1 shows a schematic partial section through an embodiment of an inventive

Fuel injector;

Fig. 2 is a schematic partial section in section II of Fig. 1 through the first embodiment of an inventive

Fuel injector;

3 shows a schematic partial section in section II of FIG. 1 through a second exemplary embodiment of a fuel injection valve according to the invention;

Fig. 4 is a schematic section in section II of Fig. 1 through a third embodiment of a fuel injector according to the invention, and

5 shows a schematic section in section II of FIG. 1 through a fourth embodiment of a fuel injection valve according to the invention.

Description of the embodiments

Before the fuel injection valves 1 according to the invention are explained in more detail with reference to FIGS. 2 to 4 To better understand the invention, the fuel injector 1 according to the invention will first be briefly explained in an overall view with regard to its essential components with reference to FIG. 1.

The fuel injection valve 1 is designed in the form of a fuel injection valve 1 for fuel injection systems of mixture-compressing, spark-ignited internal combustion engines. The

Fuel injection valve 1 is particularly suitable for injecting fuel directly into a combustion chamber (not shown) of an internal combustion engine.

The fuel injector 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. The fuel injector 1 in the exemplary embodiment is an electromagnetically actuated fuel injection valve 1, which has a spray opening 7. The nozzle body 2 is sealed by a seal 8 against the outer pole 9 of a magnetic circuit. A magnet coil 10 is wound on a coil support 12 and encapsulated by a coil housing 11. The coil carrier 12 itself rests on 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 gap 26 and are supported on a connecting 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 in a valve needle guide 14, which is disc-shaped and guided in a guide disc 31. An anchor 20 is located on the downstream side of a disk 15. This armature stands over a flange 21 non-positively connected to the valve needle 3, which is connected to the flange 21 by a weld 22. A restoring spring 23 is supported on the flange 21 and, 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 guide disk 31, which guide the fuel, which is supplied via a central fuel supply 16 and filtered by a filter element 25, to the sealing seat. The fuel injector 1 is sealed by a seal 28 against a distribution line, not shown.

In the fuel injector 1 according to the invention, in the idle state of the fuel injector 1, the armature 20 is acted upon by the return spring 23 against the stroke direction via the flange 21 on the valve needle 3 in such a way that the valve closing body 4 is held in sealing contact with the valve seat surface 6 and the valve closing body 4 is in its downstream stroke-limiting end position. When the magnet coil 10 is excited, it builds up a magnetic field which moves the armature 20 in the stroke direction counter to the spring force of the return spring 23, the stroke being predetermined by a working gap 27 in the rest position between an extension 34 and the valve seat body 5. The armature 20 takes the flange 21, which is welded to the valve needle 3, and thus also the valve needle 3 in the lifting direction. The valve closing body 4, which is operatively connected to the valve needle 3, lifts off the valve seat surface 6 and the fuel which reaches the sealing seat via the fuel channels 30a to 30c flows past the valve closing body 4 through swirl channels 33 into the spray opening 7 and is sprayed off.

If the coil current is switched off, the armature 20 falls after the magnetic field is sufficiently reduced by the pressure of the Return spring 23 on the flange 21 from the inner pole 13, whereby the valve needle 3 moves against the stroke direction. As a result, the valve closing body 4 rests on the valve seat surface 6 and the fuel injection valve 1 is closed.

An embodiment of a fuel injector 1 according to the invention is shown enlarged in FIG. 2 in area II of FIG. 1. In the idle state of the fuel injection valve 1, the valve seat body 5 forms a first stroke limitation by the valve closing body 4 resting on the valve seat surface 6. The valve seat body 5 is penetrated by an extension 34, which has a downstream radial extension 35, which forms a second stroke limitation with the valve seat body 5 when the solenoid 10 is excited.

Downstream of the valve seat surface 6, there is a through opening in the valve seat body 5, which has a contact surface 32 designed as a radial extension to the downstream side of the valve seat body 5. The extension 34 ^■ penetrates the through opening and is connected to the Ventilschließkδrper 4, for example by welding or brazing, force-fitting manner. In the extension 34, a spray opening 7 is introduced, which is connected by one or more swirl channels 33 to the gap formed between the valve closing body 4 and the valve seat surface 6 when the fuel injection valve 1 is open. To generate a swirl, the swirl channels 33 preferably have a tangential component.

Of the through-hole 37 penetrating extension 34 has a sleeve-shaped portion 36 which is sized in length so that the protrusion 34 is formed between the abutment surface 32 of the Ventilsitzkorpers 5 ^• and the radial extension in the resting state of fuel injector 1, a working gap 27th The axial extension of the working gap 27 defines the maximum stroke of the valve closing body 4 in relation to the valve seat surface 6. The radial extent of the through hole 37 is greater than the radial expansion of the sleeve-shaped portion 36 of the projection 34 upstream of its radial enlargement 35. ^'energizing the solenoid 10 of the valve closure member 4 lifts off from valve seat surface 6, and the flow path for the fuel-free. Until the upper stroke-limiting end position is reached, the fuel flows both through the swirl channels 33 and through the gap 38 formed between the valve seat body 5 and the extension 34 and is sprayed out of the spray opening 7 or the working gap 27. Towards the end of the stroke, the working gap 27 between the radial extension 35 of the extension 34 and the contact surface 32 of the valve seat body 5 is increasingly reduced and the fuel flow through the working gap 27 is reduced. When the fuel injection valve 1 is fully open, the radial extension 35 is in contact with the contact surface 32. The contact surface 32 and the radial extension 5 preferably have corresponding geometries, so that the radial extension 35 interacts with the contact surface 32 to form a sealing seat. The flow path of the fuel through the working gap 27 is now closed and, when fully opened, the entire sprayed fuel is swirled.

Furthermore, the introduction of flow-guiding elements into the contact surface 32 or into the radial extension 35 of the extension 34 is conceivable, which form a second flow path over the entire injection period. The targeted formation of a locally differently prepared fuel jet is possible.

In fuel injection valves 1, with which partial stroke operation is possible, the spray pattern can be influenced over the entire injection process. In partial stroke operation, the valve closing body 4 can be raised over only a part of the maximum possible stroke. Accordingly, the working gap 27 between the radial extension 35 and the contact surface 32 opened to different degrees and changes the amount of fuel sprayed without swirl, which leads to a change in the spray pattern.

Another embodiment of a fuel injector 1 according to the invention is shown in FIG. 3. In contrast to the exemplary embodiment in FIG. 2, the formation of a second flow path during the opening of the fuel injection valve 1 is prevented. The passage opening 37 is dimensioned relative to the sleeve-shaped section 36 of the extension 34 so that the gap 38 formed between the components is hydraulically sealed. During the opening process, the amount of fuel sprayed off is determined by the changing coverage of the swirl channels 33 by the valve seat body .5 in the region of the passage opening 37.

The swirl channels 33 are to be selected according to the desired behavior during opening. They can be introduced as bores or as slots with variable geometry. Different positioning of the individual swirl channels 33 in the flow direction is also conceivable. The complete flow cross section is thus released successively with the stroke of the valve closing body 4 and the associated extension 34.

FIG. 4 shows an embodiment with a one-piece design of valve needle 3 and extension 35 on a fuel injection valve 1 without forming a second flow path. The spherical valve closing body 4 has a central recess 40 which is penetrated by the valve needle 3. The spray opening 7 is introduced, for example, as a bore in the downstream end of the valve needle 3 in the region of the extension 34. By designing the spray opening 7 as a blind hole, the dead volume is limited and dripping of fuel after the spraying process has ended prevented. In the axial direction, the position of the valve closing body 4 is preferably fixed by welding to the valve needle 3. The welded connection 39 can be realized by welding points, which are distributed over the circumference of the valve needle 3, as well as a circumferential weld seam.

FIG. 5 shows a variant of the exemplary embodiment from FIG. 4 with a hollow valve needle 3. The valve closing body 4 is in turn pushed onto the valve needle 3 and welded. The valve needle 3 is designed as a hollow needle to reduce the moving mass. In order to prevent fuel from penetrating upstream of the sealing seat, the valve needle 3 is closed upstream. This can e.g. at their upstream end by welding. Due to the tubular geometry of the valve needle 3, there is no need to introduce the spray opening 7 in a separate manufacturing step.

Claims

Expectations

1. Fuel injector (1) for

Fuel injection systems of internal combustion engines with a valve closing body (4) which cooperates with a valve seat surface (6) of a valve seat body (5) to form a sealing seat, and with a stroke limitation of the valve closing body (4), characterized in that downstream of the sealing seat on the valve closing body

(4) an extension (34) is arranged which has a sleeve-shaped section (36) which extends through a through opening (37) in the valve seat body (5), and that the extension (34) has a radial extension at its downstream end (35) which, in the idle state, has an axial distance from a contact surface (32) in the valve seat body (5) and is greater than the smallest radial extent of the through-opening (37) and with the contact surface (32) when the fuel injection valve (1) is open. interacts to limit the stroke.

2. Fuel injection valve according to claim 2, characterized in that in the extension (34) an injection opening (7) is introduced, at least when the fuel injection valve (1) is open by at least one Swirl channel (33) is connected to a volume that is filled with fuel.

3. Fuel injection valve according to claim 1 or 2, characterized in that on the downstream side of the valve seat body (5) is formed as a radial extension bearing surface (32).

4. Fuel injection valve according to claim 2, characterized in that the swirl channels (33) with a tangential component in the spray opening (7) open into the extension (34).

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

4, characterized in that the radial extension (35) on the extension (34) and the contact surface (32) in the valve seat body (5) cooperate with a fully open fuel injector (1) to form a sealing seat.

6. Fuel injection valve according to one of claims 1 to 5, characterized in that the extension (34) with the valve closing body (4) is welded.

7.- Fuel injection valve according to one of claims 1 to 5, characterized in that the extension (34) by brazing with the

Valve closing body (4) is connected.

8. Fuel injection valve according to one of claims 1 to 7, characterized in that the swirl channels (33) are bores in the extension (34).

9. Fuel injection valve according to one of claims 1 to 7, characterized in that the swirl channels (33) in the extension (34) are slot-shaped.

10. Fuel injection valve according to one of claims 1 to 9, characterized in

^• That a gap (38) formed between the extension (34) and the valve seat body (5) is hydraulically sealed.

11. Fuel injection valve according to one of claims 1 to 10, characterized in that the extension (34) with a valve needle (3) is integrally formed.

12. Fuel injection valve according to claim 11, characterized in that the valve needle (3) penetrates the valve closing body (5).