EP1576278A1

EP1576278A1 - Fuel injection valve

Info

Publication number: EP1576278A1
Application number: EP03812123A
Authority: EP
Inventors: Wolfgang-Manfred Ruehle; Matthias Boee; Norbert Keim
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2002-12-05
Filing date: 2003-08-07
Publication date: 2005-09-21
Also published as: DE10256948A1; KR20050084098A; US20060163390A1; WO2004051073A1; JP2006509141A

Abstract

Disclosed is a fuel injection valve (1), particularly for injecting fuel directly into a combustion chamber of an internal combustion engine, comprising a valve needle (3) that is provided with a valve-closing member (4) at the injection end thereof. Said valve-closing member (4) cooperates with a valve seat area (6) that is embodied on a valve seat member (5) so as to form a sealing seat. The inventive fuel injection valve also comprises a spray port (7) that is disposed downstream of the sealing seat, and an anchor (20) which touches the valve needle (3). Said anchor (20) is arranged on the valve needle (3) so as to be movable in an axial direction between a first stop (21) that is located on the valve needle (3) and a second stop (34) while being hydraulically damped at the first stop via a pressure medium.

Description

Fuel injector

State of the art

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

For example, a fuel injector is known from DE 101 089 974 AI, in which a magnet armature engages a valve needle having a valve closing body at its spray-side end, which cooperates with a valve seat surface to form a sealing seat, the magnet armature being movable on the valve needle between one first stop of a first stop body and a second stop formed on a second stop body with a play which corresponds to the width of a gap. Due to the gap between the stops and the magnet armature and the axially freely movable magnet armature, a decoupling of the inert masses of the magnet armature on the one hand and the valve needle and the valve closing body on the other hand is achieved, since the magnetic armature can first be accelerated without the valve needle due to the force of the magnetic field. The eßdyna ik of the fuel injector is thereby improved. In the idle state, the magnet armature is underneath by a spring arranged between the first stop body and the armature Intermediate layer of an intermediate ring pressed against the second stop body. The intermediate ring, which is made of an elastomer, for example, acts as a damper against armature bumps when the fuel injector closes, which is caused by the magnet armature lagging the valve needle during the closing process, and to shorten the vibration process thereby excited. It also acts as a damping element against the bouncing processes that occur when opening, which causes the valve needle lagging the magnet armature when the second stop body impacts the magnet armature. The intermediate ring also serves to reduce the distance that the valve needle travels in the armature after reaching the upper armature stop. The time required for the fuel injector to assume a stable and vibration-free state after tightening the magnet armature or after closing the sealing seat, from which it is possible to actuate the fuel fine valve again from a precisely determinable state, is reduced by the intermediate ring ,

A disadvantage of the fuel injector described above is, in particular, that the intermediate _ring, which is made of, for example, an elastomer, can only insufficiently dampen the impact between the magnet armature and the stop body, in particular with a very high actuation frequency or very short opening times. At high actuation frequencies, an exact metering of fuel during an injection process is no longer possible, since the vibration processes that have not yet subsided have an inadmissible influence on the switching processes and can lead to uncontrollable changes in the actuation times, whereby different actuation times can disadvantageously occur between two consecutive actuations. This means that the respective injection quantities cannot be determined exactly. Another disadvantage arises from the fluctuating damping properties of the elastic intermediate ring. The minimum possible distance between two successive injection processes or the minimum possible opening time of the fuel injector thus increases.

A further disadvantage is that the intermediate ring is an additional component and complicates the production of the fuel injector.

Advantages of the invention

The fuel injector according to the invention has the advantage that the hydraulic damping measures between the armature and valve needle or the armature and the armature stops decay the vibrations faster and the necessary paths can be kept shorter. As a result, in particular the fuel injection quantity per injection process, which is reproducibly minimally possible, can be further reduced, the scatter of the injection quantity between the injection processes and between fuel injection valves of the same type being also reduced. In particular, the switching interval between two injections can thereby be significantly reduced, for example from 2 ms to less than 1 ms.

Due to the missing intermediate ring and the relief of the

Wear surfaces and the susceptibility to errors are significantly reduced. The manufacturing effort is reduced.

Advantageous further developments of the fuel injector are possible through the measures listed in the subclaims.

In a first development of the fuel injection valve according to the invention, the pressure medium, via which the first stop with the armature is hydraulic interacts, fuel or fuel used, especially diesel or gasoline. This eliminates the need for a special pressure medium and simplifies the manufacture of the fuel injector.

In a further development, the second stop is firmly connected to the valve needle or a shim. This allows the play required for the axial movement of the armature to be set precisely, simply and permanently easily.

It is also advantageous that the first stop has a first recess on its side facing the armature and / or the armature has a second recess on its side facing the first stop. As a result, hydraulically effective cavities can be generated in a simple manner, each of which interacts with the opposite component.

It is also advantageous to form the recesses in one or more stages, since this makes it easy to adjust the hydraulic effectiveness.

If the first and / or the second recess in a further development of the fuel injection valve according to the invention is delimited by the valve needle, the manufacture of the recesses is simplified, for example, since it can be produced in particular by a simple bore.

It is also advantageous to arrange a plurality of first and / or second recesses in the first stop or in the anchor. As a result, the hydraulic effectiveness in particular can be easily controlled. In addition, the arrangement and the extent of the recesses can be more easily adapted to the spatial and hydraulic conditions.

In a further development of the fuel injector according to the invention, the first stop engages in the second recess arranged in the armature and / or the armature the first recess arranged in the first stop. This makes it easier to adjust the hydraulic interaction between the anchor and the first stop.

In a further development of the armature forms, together with the first recess and / or ^'the first stop together with the second recess at least one chamber with at least one throttle point. As a result, the hydraulic effect between the anchor and the first stop can be further strengthened and its time course can be advantageously influenced.

It is also advantageous if the chamber is partially delimited by the valve needle, since this in particular simplifies the manufacture of the chamber.

If the first and / or the second recess is also circular or ring-shaped, they can be produced particularly advantageously in a simple, accurate and cost-effective manner.

drawing

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

1 shows a schematic section through a fuel injector of the generic type,

2 shows an enlarged, schematically illustrated section through a first exemplary embodiment according to the invention of fuel injector 1 in the region of armature 20,

Fig. 3 shows an enlarged cal atic section through a second invention Embodiment of the fuel injector 1 in the area of the armature 20 and

Fig. 4 is an enlarged schematic section through a third inventive

Embodiment of fuel injector 1 in the area of armature 20.

Description of the embodiment

An exemplary embodiment of the invention is described below by way of example. Matching components are provided with matching reference numerals in all figures. Before, however, exemplary embodiments of the invention are described with reference to FIGS. 2 to 4, a better understanding of the measures according to the invention is first made with reference to FIG. 1 a generic

Fuel injection valve according to the prior art briefly explained in its essential components.

A fuel injector 1 shown in FIG. 1 is designed in the form of a high-pressure fuel injector 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 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, the fuel injection valve 1 is a fuel injection valve 1 that opens inwards 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 in a coil housing 11 encapsulated and wound on a coil support 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 connected to one another by a non-ferromagnetic 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 guided in a valve needle guide 14, which is disc-shaped. A paired adjusting washer 15 is used for stroke adjustment. The armature 20 is located on the other side of the adjusting washer 15. This armature is non-positively connected via a first stop 21 to the valve needle 3, which is connected to the first stop by a first joint connection 22 in the form of a weld seam 21 is connected. A restoring spring 23 is supported on the first stop 21, which in the present design of the fuel injector 1 is preloaded by a sleeve 24.

Fuel channels 30, 31 and 32 run in the valve needle guide 14, in the armature 20 and on a guide element 36. 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 further seal 37, against a cylinder head, not shown.

On the spray-side side of the armature 20, a gap 33 is provided between the armature 20 and a second stop 34, which gap can accommodate an annular damping element (not shown) made of elastomer material. The armature 20 is guided on the valve needle 3 so as to be axially movable between the second stop 34 and the first stop 21. The second stop 34 is in this embodiment of a generic fuel injector 1 is connected to the valve needle 3 via a second joint 35 in the form of a weld.

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. The gap 33 is closed, i. H. the armature 20 and the second stop 34 touch each other unless there is an annular damping element in the intermediate layer. When the gap 33 is closed, an anchor free path 44, shown in greater detail in FIGS. 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. At the same time, a spring element 38 shown in FIGS. 2 to 4, which engages the first stop 21 and is supported on the armature 20, is further tensioned, which in the rest position presses the armature 20 against the second stop 34 with a prestress and thereby presses against the first stop 21 trained shoulder 40 supports.

The return spring 23 is also supported on the shoulder 40, the shoulder 40 being arranged on the side of the stop 21 facing away from the armature 20. The spring element 38 shown in FIGS. 2 to 4 is also referred to as an AFW spring or an anchor free travel spring. The armature 20 takes the first stop 21, which is welded to the valve needle 3, after passing through the armature free path 44 shown in FIGS. 2 to 4, likewise in the stroke direction. The valve closing body 4 connected to the valve needle 3 lifts off from the valve seat surface 6, and the fuel passed through the fuel channels 30 to 32 is sprayed off through the spray opening 7. If the coil current is switched off, the armature 20 of the magnetic field falls sufficiently decayed by the pressure of the return spring 23 from internal pole 13, whereby the standing with the valve needle 3 2 ₁ first stopper moves against the stroke direction. The valve needle 3 is thereby moved in the same direction, as a result of which the valve-closure member 4 is seated on the valve seat surface 6 and the fuel injector 1 is closed.

FIG. 2 shows an enlarged, schematically illustrated section through a first exemplary embodiment according to the invention of the fuel injector 1 shown in FIG. 1 in the area of the armature 20. FIG. 2 shows the fuel injector 1 in the idle state with the sealing seat closed. 2 clearly shows the spring element 38, which in the illustrated state presses the armature 20 against the second stop 34, which in this exemplary embodiment is connected to the adjusting disk 15, for example. The anchor free path 44 is maximally formed in this state. The first stop 21 engages in a step-shaped second recess 41 arranged on the armature 20, which is partially delimited by the valve needle 3.

Through the engagement of the first stop 21 in the second recess 41, a chamber 42 is formed at the spray-side end of the second recess 41. A throttle point 43 is formed between the chamber 42 and the side of the armature 20, around which fuel flows around, and which in this exemplary embodiment runs parallel to the longitudinal axis of the valve needle 3 between the armature 20 and the part of the first stop 21 which engages in the recess 41. The width and thus part of the hydraulic effect of the throttle point 43 is determined in particular by the inside diameter of the second recess 41 and the outside diameter of the first stop 21 engaging in the second recess 41. •. The way it works is as follows:

Starting from the idle state shown in FIG. 2, the armature 20 5 is moved in the stroke direction, for example by electromagnetic forces, to open the fuel injection valve 1. Since the force of the return spring 23 is greater than that of the spring element 38, the armature 20 initially moves freely, without taking the valve needle 3 with it, in the stroke direction and builds up kinetic energy. After passing through the armature free path 44, that is to say when the end of the first stop 21 facing the armature 20 touches the armature 20 or the second recess 41, the armature 20 takes the first stop 21 and thus the valve needle 3 in the stroke direction until the armature 20 has passed the path defined by the working gap 5 27 and strikes the inner pole 13.

Due to its own kinetic energy, however, the valve needle 3 initially moves further in the stroke direction against the force of the return spring 23, as a result of which a vacuum is created in the chamber 42, since fuel cannot flow through the throttle point 42 quickly enough. This negative pressure also counteracts the movement of the valve needle 3 in the stroke direction and 5 shortens the distance that the valve needle 3 travels after the armature 20 strikes the inner pole. This path is also known as the tunnel tunnel. The kinetic energy which the valve needle 3 builds up due to the force of the return spring 23 during the movement against the stroke direction 0 is thus reduced, and thus also the risk of the armature 20 coming loose from the inner pole 13. In addition, it provides for the chamber 42 through the throttle point 43 flowed fuel for a damped movement of the valve needle 3 against the stroke direction, which further reduces the risk of the armature 20 becoming detached from the inner pole 13.

To close the fuel injector 1, the magnetic circuit is interrupted and the armature 20 is released from the inner pole 13. Due to the force of the return spring 23 now move the first stop 21, the valve needle 3 and the armature 20 against the stroke direction. First, the valve needle 3 with its valve closing body 4 is seated on the valve seat surface 6. The armature 20, which is axially freely movable on the valve needle 3, moves further around the armature free path 44 before it strikes the second stop 34. The negative pressure building up in the chamber 42 brakes the armature 20 as it runs through the armature free path 44. This reduces the momentum which acts on the armature 20 when it hits the second stop 34. In addition, the vibration process triggered by the pulse is damped by the hydraulic damping effect of the chamber 42 and the throttle point 43 and is shortened in time and its amplitude is reduced. As a result, the fuel injection valve 1 can be actuated again from a vibration-free and stable state after only a short time, as a result of which precisely determinable and exactly reproducible injection quantities can be implemented even with very short actuation intervals.

FIG. 3 shows an enlarged, schematically illustrated section through a second exemplary embodiment according to the invention in the area of the armature 20, similar to the first exemplary embodiment from FIG. 2. In contrast to the first exemplary embodiment from FIG. 2, the first stop 21 also has on its side facing the armature 20 Page a first recess 39. Due to the enlarged chamber 42, the hydraulic properties can advantageously be easily adjusted.

FIG. 4 shows an enlarged, schematically illustrated section through a third exemplary embodiment according to the invention in the area of the armature 20, similar to the first exemplary embodiment from FIG. 2. In contrast to the first exemplary embodiment from FIG. 2, a first recess 39 is arranged only in the first stop 21. The throttle point 43 is arranged between the end of the first stop 21 facing the armature 20 and the end of the armature 20 facing the first stop 21. This The embodiment is particularly suitable for fuel injection valves 1 which have a large, radially extending space in the area of the armature 20, since the damping effect is set in particular over the length of the throttle point 43 which runs radially in this exemplary embodiment. The manufacturing outlay is advantageously reduced.

The invention is not limited to the illustrated embodiments and z. B. can also be used for outward opening fuel injection valves.

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) at its spray-side end, which has a valve seat surface (6) on a valve seat body (5) is configured to work together to form a sealing seat, at least one spray opening (7) provided downstream of the sealing seat and an armature (20) engaging on the valve needle (3), the armature (20) being arranged between one on the valve needle (3) the first stop (21) and a second stop (34) are arranged so that they can move axially on the valve needle (3), characterized in that the armature (20) on the first stop (21) is hydraulically damped by a pressure medium.

2. Fuel injection valve according to claim 1, characterized in that the pressure medium is fuel, in particular gasoline or diesel fuel.

3. Fuel injection valve according to claim 1 or 2, characterized in that the second stop (34) is fixedly connected to the valve needle (3) or a shim (15) or fixed to the housing.

4. Fuel injection valve according to one of claims 1 to 3, characterized in that the first stop (21) on its side facing the armature (20) has a first recess (39) and / or the armature (20) on its first stop (21) facing side has a second recess (41).

5. Fuel injection valve according to claim 4, characterized in that the first recess (39) and / or the second recess (41) are formed in one or more stages.

6. Fuel injection valve according to claim 4 or 5, characterized in that the first recess (39) and / or the second recess (41) are partially limited by the valve needle (3).

7. Fuel injection valve according to one of claims 4 to 6, characterized in that the first stop (21) has a plurality of first recesses (39) and / or the armature (20) has a plurality of second recesses (41).

8. Fuel injection valve according to one of claims 4 to 7, characterized in that the first stop (21) engages in the armature (20) arranged second recess (41) and / or the armature (20) in the first stop (21st ) arranged first recess (39) engages.

9. Fuel injection valve according to one of claims 4 to 8, characterized in that the armature (20) together with the first recess (39) and / or the first stop (21) together with the second Recess (41) forms at least one chamber (42) with at least one throttle point (43).

10. Fuel injection valve according to claim 9, characterized in that the chamber (42) is partially delimited by the valve needle (3).

11. Fuel injection valve according to one of claims 4 to 10, characterized in that the first recess (39) and / or the second recess (41) are circular or annular.