EP2021617B1 - Fuel injector comprising a pressure-compensated control valve - Google Patents

Abstract

In a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine, an injection valve member for opening and closing at least one injection opening is triggered by a control valve embodied as a magnet valve. On the armature of the magnet valve, a sealing face is embodied that for closing the control valve is positionable into a valve seat. The armature of the magnet valve is movable, without armature guidance, between an upper and a lower stroke stop. Because the sealing face, which for closing the control valve is positionable into the valve seat, is embodied on the armature, an additional closing element of the kind provided in the prior art can be dispensed with.

Description

State of the art

The invention relates to an injector for injecting fuel into a combustion chamber of an internal combustion engine according to the preamble of claim 1, such as in WO 03/002868 or EP 1319827 Tide.

An injector for injecting fuel into a combustion chamber of an internal combustion engine, in which an injection valve member is actuated via a solenoid-operated control valve is for example off EP-A 1612 403 known. With the help of the control valve, a flow restrictor from a control room in the fuel return can be closed or released. The control chamber is bounded on one side by a control piston with which an injection valve member is actuated, which releases or closes at least one injection opening into the combustion chamber of the internal combustion engine. The outlet throttle is received in a body, which is provided on the side facing away from the control chamber with a tapered valve seat. In this valve seat, a closing element is adjustable, which is connected to the armature of the solenoid valve. For this purpose, an edge is formed on the closing element, which is provided against the conically shaped seat. The closing element moves on an axial rod, which is integrally connected to the body in which the drainage throttle is formed.

For the valve to close in a liquid-tight manner, it is necessary to produce high-precision surfaces and to provide a high-precision fit of the closing element on the axial rod. As a result, the closing element is exactly guided and thus ensured that it seals the seat liquid-tight.

Disclosure of the invention

In an inventively designed fuel injector for injecting fuel into a combustion chamber of an internal combustion engine is an injection valve member for releasing and closing at least one injection port by a solenoid valve trained control valve controlled. At the armature of the solenoid valve, a sealing surface is formed, which is adjustable for closing the control valve in a valve seat. The armature of the solenoid valve is movable without an armature guide between an upper and a lower stroke stop. Characterized in that the sealing surface is formed on the armature, which is adjustable for closing the control valve in the valve seat, can be dispensed with an additional closing element, as provided in the prior art. This minimizes the mass of moving components. By minimizing the mass of the moving components, shorter switching times can be realized. Another advantage of forming the sealing surface directly at the armature of the solenoid valve is that the solenoid valve thereby requires little space.

A liquid-tight closure of the solenoid valve by the sealing surface is placed on the anchor in the valve seat, is achieved by the fact that the sealing surface is aligned with the anchor on the lower stroke stop. This alignment takes place in a preferred embodiment by means of a resilient guide lip, which is formed on the armature. The guide lip is preferably formed on the outer diameter of the armature. If the anchor begins to wobble during the closing movement, the anchor will first strike with the guide lip. In the further movement is characterized in that the guide lip is designed resiliently, the armature aligned so that the sealing surface rests flat on the valve seat and thus a liquid-tight connection is generated. The movement of the armature in the lower stroke stop is carried out by means of a spring element. The spring element is preferably a helical spring designed as a compression spring. Thus, the introduction of force as close as possible in the region of the valve seat, the inner diameter of the spring element preferably corresponds substantially to the inner diameter of the valve seat. Due to the elasticity of the resilient guide lip is achieved that is lost to this little of the spring force of the spring element.

In a preferred embodiment, the guide lip and the sealing surface on the armature and the stop surface and the valve seat of the control valve are ground to the same height. As a result, the valve seat of the solenoid valve can be manufactured cost-effectively, since the pairing with a second component is eliminated.

The upper stroke stop is preferably formed by an annular surface. By hitting the ring surface, the anchor, which can get into tumbling during the flight phase, aligns again.

In order to achieve an axial pressure equalization, the armature is designed so that the respective opposite surfaces on which an axial compressive force acts are the same size and are acted upon by the same pressure. To achieve this, the anchor is a Run bore whose diameter corresponds substantially to the inner diameter of the valve seat. To accommodate the pressure forces a push rod is received in the bore. In order to minimize the fuel leakage through the gap between the bore and the push rod, the bore is honed in a preferred embodiment. Also, the push rod and the bore are made in a tight leadership game. However, it is not necessary to fabricate the bore and the sealing surface on the anchor in a clamping to obtain a precise right-angled alignment of sealing surface and bore. As a result, the production of the armature is simplified.

In general, the abutment surface for the resilient guide lip and the valve seat are formed on a valve piece. This is accommodated in the injector housing. By forming the abutment surface and the valve seat on the valve piece, it is possible to produce them on an outer surface. It is not necessary to just grind an end face of a hole.

The spring force of the spring element, by which the movement of the armature is supported by the magnet in the valve seat, is preferably adjusted by a disc. This is done by the spring element is biased by the disc. The larger the axial extent of the disc, the stronger the spring element is biased and the greater the spring force acting on the anchor.

In general, the disc is arranged on the side facing away from the armature of the spring element. In a preferred embodiment, however, the disc is arranged between the spring element and the armature. Advantage of this arrangement is that the disc with which the spring force is adjusted, so can be used in addition to the centering of the armature.

In order to avoid that the armature canted during the opening or closing movement, the push rod in another embodiment comprises a pressure pin and a bolt, wherein the bolt is received in the bore in the armature and the pressure pin is enclosed by the spring element. The tilting is avoided in particular by the fact that the bolt is tiltable relative to the pressure pin. This is achieved, for example, in that the mutually facing ends of the pressure pin and the bolt are crowned, ie preferably in the form of a spherical section. Alternatively, it is also possible to take a ball between the pressure pin and the bolt. Also, any further, known in the art design is possible, with which the bolt can be bent relative to the pressure pin from the axial alignment.

drawing

• Figur 1 einen Ausschnitt aus einen Kraftstoffinjektor mit einem erfindungsgemäß ausgebildeten Magnetventil in einer ersten Ausführungsform,
• Figur 2 ein erfindungsgemäß ausgeführtes Magnetventil in einer zweiten Ausführungsform,
• Figur 3 ein erfindungsgemäß ausgeführtes Magnetventil in einer dritten Ausführungsform.

In the following the invention will be described in more detail with reference to a drawing.
It shows:

• FIG. 1 a detail of a fuel injector with an inventively designed solenoid valve in a first embodiment,
• FIG. 2 a solenoid valve according to the invention in a second embodiment,
• FIG. 3 an inventively designed solenoid valve in a third embodiment.

embodiments

FIG. 1 shows a section of an inventively designed fuel injector with solenoid valve in a first embodiment.

In a fuel injector 1 designed according to the invention, a control piston 2 with which an injection valve member, not shown here, is actuated, is actuated by a solenoid valve 3. At least one injection opening is released or closed by the injection valve member, thus controlling the injection of fuel into a combustion chamber of an internal combustion engine.

The movement of the control piston 2 takes place hydraulically. For this purpose, the control piston 2 opens with the side facing away from the injection valve member in a control chamber 4. About an inlet throttle 5, the control chamber 4 is connected to a fuel inlet 6. As a result, fuel under system pressure can flow into the control chamber 4. About an outlet throttle 7, the control chamber 4 is relieved. For this purpose, the outlet throttle 7 with an in FIG. 1 not shown return hydraulically connected. In order to fill the control chamber 4 with fuel under system pressure, the outlet throttle 7 can be closed by means of the solenoid valve 3. For this purpose, in the inventively embodied solenoid valve 3, a sealing surface 8, which is formed on the armature 9 of the solenoid valve 3, placed in a valve seat 10. In the embodiment shown here, the sealing surface 8 and the valve seat 10 form a flat seat. However, it is also conceivable any further, known in the art valve seat, in which no axial forces acting on the closing element.

In order to receive the pressure force acting in the axial direction when the solenoid valve 3 is closed, a bore 11 is formed in the armature 9, in which a pressure rod 12 is received. So that no axial pressure forces act on the armature 9 when the valve is closed, the diameter of the bore 11 is substantially equal to the inner diameter of the sealing surface 8. Another object of the push rod 12 is to seal the bore 11 against leakage currents. For this reason, it is necessary that the push rod 12 and the bore 11 are made in a close guide play. Compared with the known from the prior art fuel injectors, however, it is not necessary to manufacture the bore 11 and the sealing surface 8 on the armature 9 in a clamping in order to obtain a precise rectangular alignment of the sealing surface 8 and 9 hole. As a result, the manufacture of the armature 9 is simplified.

To move the armature 9 at the lower stroke stop, i. When the sealing surface 8 is in the valve seat 10 to align, an elastic guide lip 13 is formed on this. The upper stroke stop of the armature 9 is formed by an annular surface 14, which is designed as a lower end face of a Hubanschlaghülse 15.

In the embodiment shown here, a bore 16 is formed in the Hubanschlagshülse 15, in which a spring element 17 is received. The spring element 17 is preferably designed as a compression spring coil spring which is supported on one side of the armature 9 and the other side on a disc 18. The disc 18 is placed against an end face 19 of the bore 16. By means of the axial extent of the disc 18, the spring force can be adjusted, with which the spring element 17 acts on the armature 9.

Furthermore, the solenoid valve 3 comprises a magnet 20 which is accommodated in a magnetic core 21. The power supply of the magnet 20 via pins 28th

In order to achieve a flat support of the sealing surface 8 on the armature 9 on the valve seat 10, the valve seat 10 and a support surface 22 on which the elastic guide lip 13 rests when the armature 9 is located at the lower stroke stop, ground to a height. Likewise, the support of the elastic guide lip 13, which rests on the support surface 22 and the sealing surface 8 ground on the armature 9 to a height.

The stroke of the armature 9 is limited by the Hubanschlaghülse 15. To adjust the stroke, the armature 9 and the magnetic core 21 are enclosed by a sleeve 23, by the axial extent of the stroke is determined. To adjust the stroke is the Hubanschlaghülse 15 with an end face 24 on the sleeve 23 on this.

The inlet throttle 5, the outlet throttle 7 and the valve seat 10 and the bearing surface 22 are formed on a valve piece 25 which is received in the injector 26. The attachment of the valve piece 25 in the injector 26 by means of a valve clamping screw 27th

To guide the pins 28 through the Hubanschlaghülse 15, a bore 29 is formed in this for each pin 28. For sealing and centering of the pins 28 of the bore 29, the pins 28 are each surrounded by a lower disc 30, an upper disc 31 and an intermediate sealing ring 32.

The attachment of Hubanschlaghülse 15 on the injector 26 takes place in the embodiment shown here by means of a clamping nut 33rd

The inventively embodied solenoid valve 3 can be used both inversely controlled fuel injectors as well as not inversely controlled fuel injectors.

To start the injection process, the magnet 20 of the solenoid valve 3 is energized in a non-inversely controlled fuel injector. Not inverted means that when energized magnet 20, the at least one injection port is released and fuel is injected into the combustion chamber of the internal combustion engine. By energizing the magnet 20, a magnetic field is formed, through which the armature 9 is attracted by the magnet 20 and thus moves in the direction of the magnet 20. As a result, the sealing surface 8 of the armature 9 lifts out of the valve seat 10 and a connection from the control chamber 4 via the outlet throttle 7 in the return, not shown here is released. Due to the released connection, fuel can drain from the control chamber 4. This leads to a pressure drop in the control chamber 4. Due to the pressure drop in the control chamber 4, the pressure force which acts on the control piston 2 decreases and the control piston 2 is moved into the control chamber 4. As a result of this movement of the control piston 2, the injection valve member lifts out of its seat and thus releases the at least one injection opening. The injection process begins.

The stroke of the armature 9 is limited by the Hubanschlaghülse 15 by the armature 9 abuts against the annular surface 14 of the Hubanschlaghülse 15.

An axial guidance of the armature 9 is effected by an extension 34 on the armature 9, which is guided in the bore 16 of the Hubanschlaghülse 15. In order to produce the fuel injector low, however, the holes 16 and the extension 34 are not mating ground on anchor 9, so that despite the small stroke, generally in the range between 0.02 to 0.04 millimeters, a tumbling of the armature 9 is not can be prevented.

In order to ensure when closing the outlet throttle 7, whereby the injection process is terminated, to ensure that the sealing surface 8 is placed liquid-tight in the valve seat 10 on the armature 9, the resilient guide lip 13 is formed on the armature 9. Due to the resilient guide lip 13, the armature 9 is prevented from tilting even when the spring force of the spring element 17 acts unevenly on the armature. If there is a tilting of the armature 9, the resilient guide lip 13 abuts against the support surface 22 and thereby prevents further tilting of the armature. 9

To end the injection process, the energization of the magnet 20 is stopped. With the aid of the spring element 17, the armature 9 is moved away from the magnet, so that the sealing surface 8 is placed in the valve seat 10. The outlet throttle 7 is thereby closed. In the control chamber 4, which is filled via the fuel inlet 6 and the inlet throttle 5 with fuel under system pressure, system pressure builds up again. As a result, the pressure force acting on the control piston 2 increases. The control piston 2 is moved in the direction of the injection valve member and thus results in that the injection valve member is placed in its seat and thus closes the at least one injection opening.

An inversely controlled fuel injector differs from the non-inversely controlled fuel injector in that, when the magnet is energized, the at least one injection opening is closed and the at least one injection opening is released when the magnet is not energized. For this purpose, the control piston 2 and the injection valve member are coupled to each other hydraulically, which is lifted in a movement of the control piston 2 in the direction of the injection valve member from the seat and the at least one injection opening releases and is energized with energized magnet of the control piston 2 in the direction of the control chamber 4 , whereby the injection valve member is placed in its seat and closes the at least one injection opening.

In FIG. 2 is a second embodiment of an inventively designed solenoid valve 3 is shown. In the FIG. 2 illustrated embodiment differs from the in FIG. 1 illustrated embodiment in that a disc 35, with which the spring force of the spring element 17 is adjusted, is received between the spring element 17 and the armature 9. Thus, the spring element 17 is supported with one side against the disc 25 and with the other side against the end face 19 of the bore 16. By the in FIG. 2 The centering of the armature 9 is required so that it does not move radially and so the sealing surface 8 is no longer placed on the armature 9 on the valve seat 10 when the outlet throttle 7 is closed.

FIG. 3 shows a solenoid valve 3 in a third embodiment.

In the FIG. 3 illustrated embodiment differs from the in FIG. 1 illustrated embodiment in that the push rod 12 comprises a bolt 36 and a pressure pin 37. The bolt 36 is guided in the bore 11 in the armature 9.
Characterized in that the push rod 12 includes the pressure pin 37 and the bolt 36, it is avoided that the armature 9 can tilt on the push rod 12 when it begins to wobble due to uneven application of force by the spring element 17. For this purpose, the bolt 36 and the pressure pin 37 are designed so that the bolt 36 can tilt over the pressure pin 37 from the axial direction. For this purpose, at least either the pressure pin 37 on the side facing the bolt 36 or the bolt 36 on the side facing the pressure pin 37 is preferably provided with a crowned end face. In this case, having a spherical design means that the end face is designed in the form of a spherical segment, a paraboloid or a hyperboloid. In a preferred embodiment, both the end face of the pressure pin 37 facing the pin 36 and the end face of the pin 36 facing the pressure pin 37 are crowned.

In a further embodiment, a ball is received between the bolt 36 and the pressure pin 37. In this case, the ball performs the same task as the spherically shaped facing end faces of the bolt 36 and the pressure pin 37th

Task of the push rod 12 is in all three embodiments, as shown in the Figure 1 to 3 are shown to absorb axial compressive forces. For this purpose, the push rod 12 is supported against the end face 19 of the bore 16 in the Hubanschlaghülse 15. As a result, the pressure force exerted on the push rod 12 is transmitted to the Hubanschlagshülse 15.

In addition to the in Figure 1 to 3 illustrated embodiments, in which the spring element 17 and the disc 18 and the push rod 12 are supported against the end face 19 of the bore 16 in the Hubanschlaghülse 15, it is also possible that the bore 16 completely passes through the Hubanschlagshülse and the disc 18 and Support the spring element 17 and the push rod 12 directly on the injector. In this case, the bore 16 is closed by the injector housing.

LIST OF REFERENCE NUMBERS

1

fuel injector

2

spool

3

magnetic valve

4

control room

5

inlet throttle

6

Fuel supply

7

outlet throttle

8th

sealing surface

9

anchor

10

valve seat

11

drilling

12

pushrod

13

elastic guide lip

14

ring surface

15

stroke stop sleeve

16

drilling

17

spring element

18

disc

19

face

20

magnet

21

magnetic core

22

bearing surface

23

shell

24

face

25

valve piece

26

injector

27

Valve clamping screw

28

pen

29

drilling

30

lower disc

31

upper disc

32

seal

33

voltage mother

34

extension

35

disc

36

bolt

37

pushpin

Claims (10)

1. Fuel injector for injecting fuel into a combustion chamber of an internal combustion engine, in which fuel injector an injection valve member is actuated by a control valve, designed as a solenoid valve (3), in order to open and close an injection opening, and an armature (9) of the solenoid valve is movable between an upper and a lower stroke stop, wherein, for the closure of the control valve, a sealing surface (8) formed on the armature (9) interacts with a valve seat (10), characterized in that the armature (9) has a bore (11) which substantially corresponds to the inner diameter of the valve seat (10) and in which a pressure rod (12) is guided with a close fit such that the pressure rod (12) absorbs the acting axial pressure forces.
2. Fuel injector according to Claim 1, characterized in that a resilient guide lip (13) is formed on the armature (9), which guide lip, at the lower stroke stop, rests on a contact surface (22) such that the armature (9) is aligned.
3. Fuel injector according to Claim 2, characterized in that the guide lip (13) and the sealing surface (8) on the armature (9) and the contact surface (22) and the valve seat (10) of the control valve are ground to the same height.
4. Fuel injector according to one of Claims 1 to 3, characterized in that the upper stroke stop is formed by an annular surface (14).
5. Fuel injector according to one of Claims 2 to 4, characterized in that the contact surface (22) and the valve seat (10) are formed on a valve piece (25).
6. Fuel injector according to one of Claims 1 to 5, characterized in that the spring force of a spring element (17) which assists the movement of the armature (9) from the magnet (20) into the valve seat (10) is set by means of a disc (18).
7. Fuel injector according to Claim 6, characterized in that the disc (18) is held between the armature (9) and the spring element (17) and is thus additionally used for centring the armature (9).
8. Fuel injector according to one of Claims 1 to 7, characterized in that the pressure rod (12) comprises a pressure pin (37) and a stud (36), wherein the stud (36) is held in a bore (11) in the armature (9) and the pressure pin (37) is surrounded by the spring element (17).
9. Fuel injector according to Claim 8, characterized in that those ends of the stud (36) and of the pressure pin (37) which face towards one another are of spherical design.
10. Fuel injector according to Claim 8, characterized in that a ball is held between the stud (36) and the pressure pin (37).

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