EP1607620A1 - Fuel injector with clamping sleeve as a stop for a valve needle - Google Patents

Abstract

The injector has a control valve (1) with an electromagnetically valve needle (3), in which a coil (19) is received in a magnet cup (18) made of magnetizable material. A clamping sleeve (23) is received in the magnet cup, where the clamping sleeve has a gaplike opening extending between its face ends. The sleeve is braced by a spring force against a bore present in the magnet cup. An independent claim is also included for a method of producing a fuel injector in an internal combustion engine.

Description

Technical area

For fuel supply of internal combustion engines are today often fuel injectors used. For compliance with emission limit values and for the It is necessary to reduce the fuel consumption in the individual fuel consumption Cylinder is injected, is precisely measured. Extremely short opening and closing times of the injection valve required. Furthermore, the valve needle each time you open the same stroke, to ensure that the same Fuel quantity is injected into the cylinder. This is done by a stroke limitation realized.

State of the art

With the fuel injectors available on the market, the limitation of the stroke of the Valve needle in different ways.

Thus, the stroke limitation, for example, by the use of a stop washer on which the valve needle abuts realized. The stop disc lies on the magnet pot on, so that a direct impact of the valve needle on the magnet pot avoided becomes. The required for the operation of the fuel injector stroke and the residual air gap are adjusted by grinding in protrusions or steps on the valve needle.

Another way to realize the stroke limitation is that the valve needle abuts against a sleeve pressed into the magnet pot. In this variant will be the stroke and the residual air gap are adjusted by shims whose thickness is equal to the stroke or the residual air gap is adjusted.

The use of a hold-down with a sleeve-shaped stop, the magnet pot surrounded, offers another way to realize the stroke limitation. One Such sleeve-shaped stop is known from DE 102 49 161 B3. This is the hub adjusted by a shim between the valve body and the hold-down and the residual air gap by grinding the sleeve formed as a stop on the appropriate Length.

To avoid eddy currents in the magnetic pot, the switching process of the fuel injector delay, the magnet pot is described as described in Bosch Research Info, 3/2001, made of a metal / polymer composite. These are fine iron particles wrapped in plastic, pressed and sintered into a workpiece. This material is however very brittle and therefore sensitive to impact. For this reason, it must be avoided that the valve needle strikes the magnet pot.

By striking the valve needle to the magnet pot parts can break, causing the magnetic properties of the magnet pot can change. Also can the erupted particles cause higher wear and thereby to Failure of the fuel injector lead.

Presentation of the invention

In order to prevent a striking of the valve needle to the magnet pot is in the invention trained fuel injector, which has a control valve with an electromagnetic operable valve needle is driven, wherein a coil in a magnetizable from Material made magnetic pot is added, in the magnet pot one Clamping sleeve received with a running between the end faces gap-shaped opening.

For assembly, the clamping sleeve is biased and into a bore, preferably centered in the magnet pot is inserted. Due to the bias creates a spring force in the clamping sleeve, through which the clamping sleeve against the wall of the bore is pressed and holds in the magnetic pot. The spring force is calculated so that the clamping sleeve not due to the shaking stress occurring during operation and the own mass dissolves. The required extrusion forces of the clamping sleeve from the magnet pot are preferably in the range of 100 to 500 N. As Auspresskraft while the power is too understand that is required to release the clamping sleeve from the magnet pot.

In a preferred embodiment, the clamping sleeve is made of a non-magnetizable Material made. A sleeve of magnetizable material has the disadvantage that, too after completion of the power supply of the coil, the magnetization is maintained and so the Valve needle is first held by the clamping sleeve in the open position and only closes with a delay. Furthermore, the material from which the clamping sleeve is made, preferably not deformable by the impact of the valve needle. A plastic deformation The clamping sleeve would cause the needle stroke with the operating time of the fuel injector increases. An enlargement of the needle stroke can, for example to an increase in the injected fuel quantity and thus to a higher Fuel consumption lead. A suitable material for the production of the clamping sleeve is for Example carbon steel.

So that the valve needle does not hit the magnetic pot during opening, the outer diameter is the clamping sleeve preferably greater than or equal to the diameter of the stop surface the valve needle. Characterized in that the width of the extending between the end faces slit-shaped opening is at most 25% of the sleeve circumference, a kinking the valve needle when striking avoided and thus achieved a precise opening. A annular stop surface and thus a uniform striking of the valve needle can be achieved in that received in the magnet pot at least two clamping sleeves are, whose extending between the end faces gap-shaped openings at different Radial positions are arranged.

In a further preferred embodiment, the length of the clamping sleeve corresponds to Height of the magnet pot, so that the front sides of clamping sleeve and magnet pot a smooth Form surface. This is achieved in that first the at least one clamping sleeve in the magnetic pot is pressed and then the front sides of the magnet pot with the be pressed flat in this press-fitted clamping sleeve. The residual air gap required for this is that the armature of the valve needle does not stick to the magnet pot is thereby achieved that the stop surface of the valve needle to the height of the residual air gap from the Anchor of the valve needle protrudes.

drawing

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

Figur 1

ein erfindungsgemäß ausgebildetes Steuerventil eines Kraftstoffinjektors,

Figur 2

Einzelheit Z aus Figur 1,

Figur 3

eine Draufsicht auf einen Magnettopf mit darin aufgenommener Spannhülse,

Figur 4

einen Schnitt durch einen Magnettopf mit darin aufgenommener Spannhülse vor dem Planschleifen der Stirnseiten,

Figur 5

einen Schnitt durch einen Magnettopf mit darin aufgenommener Spannhülse mit plangeschliffenen Stirnseiten,

Figuren 6.1, 6.2 und 6.3

verschiedene Ausführungen der zwischen den Stirnseiten verlaufenden spaltförmigen Öffnung der Spannhülse,

Figur 7

Draufsicht auf einen Magnettopf mit zwei darin aufgenommenen Spannhülsen.

It shows:

FIG. 1

an inventively designed control valve of a fuel injector,

FIG. 2

Detail Z of Figure 1,

FIG. 3

a top view of a magnetic pot with it accommodated clamping sleeve,

FIG. 4

a section through a magnet pot with it accommodated clamping sleeve before the surface grinding of the end faces,

FIG. 5

a section through a magnet pot with it accommodated clamping sleeve with flat-ground end faces,

Figures 6.1, 6.2 and 6.3

various embodiments of the running between the end faces gap-shaped opening of the clamping sleeve,

FIG. 7

Top view of a magnetic pot with two accommodated therein clamping sleeves.

variants

Figure 1 shows an inventively designed control valve of a fuel injector.

A control valve 1 comprises a valve body 2 with a centrally located therein Hole in which a valve needle 3 is guided. On the one injector, not shown here facing side joins the valve body 2 a stop plate 4 at. On the stop plate 4 side facing the hole opens in the valve body. 2 in a first valve chamber 5. The first valve chamber 5 is formed by an end face 6 of the stop plate 4 limited. At the first valve chamber 5, a bore 10 closes in the Stop plate 4 on. The bore 10 opens a second valve chamber 8. By a Flat seat 7 on the valve needle 3, the bore 10 can be opened in the stop plate 4 or be closed.

To the injection valve, not shown in Figure 1 in the correct position to the control valve 1, a guide pin 9 is formed on the stop plate 4. to Assembly of the guide pin 9 in a corresponding bore on the injection valve introduced. In this way it is ensured that, for example, the holes for through several components passing channels aligned in the assembled fuel injector are formed.

On the side facing away from the stop plate 4, the valve needle expands into a valve pin head 11. At the valve needle head 11, a guide pin 12 connects. Of the Guide pin 12 is formed by a preferably designed as a spiral spring closing element 13 enclosed. The closing element 13 is supported with one side against an end face 14 of the valve needle head 11 and with the other side against an end face 16 of a Upper housing part 15 from. By the guide pin 12 prevents the Closing element 13 on the end face 14 of the valve needle head 11 can slip. Also the guide pin 12 prevents buckling of the closing element 13 during a lifting movement the valve needle 3 from the flat seat. 7

The valve body 2 and the upper housing part 15 are connected by a clamping nut 17 with each other connected.

The opening and closing operation of the valve needle 3 is electromagnetically controlled. For this purpose, located in the valve body 2, a magnet pot 18, which has a ring-shaped Has groove in which a coil 19 is received. The coil 19 is connected via an electrical Terminal 20 is powered. Once a voltage is applied to the coil 19 is, forms around the coil 19, a magnetic field. This magnetic field is the Magnetic pot 18 magnetized material. This causes a magnetic from Material manufactured anchor 21, which surrounds the valve needle head 11, through the magnet pot 18 is attracted. In this way, the valve needle 3 moves in the direction of Magnet pot 18 and thus releases the flat seat 7. This is designed as a spiral spring Closing element 13 compressed. The closing element 13 is within a bore 22 arranged in the magnetic pot 18, so that the magnet pot 18, the closing element 13th encloses.

The material of the magnetic pot 18 is preferably a sintered metal or contains fine Plastic coated iron particles that were pressed into a magnet pot 18. hereby prevents eddy currents in the magnet pot, which delay the switching process. This material is extremely brittle and therefore impact-sensitive. Therefore it could by striking the valve needle 3 for breaking individual particles from the magnet pot 18 come. This changes the magnetic properties. moreover The broken particles can cause higher wear and thus to Failure of the control valve 1 lead. To absorb the impact load caused by the impact the valve needle 3 is a clamping sleeve 23 is received in the bore 22 in the magnet pot 18. The clamping sleeve 23 has a gap-shaped opening extending between the end faces 24 on. The gap-shaped opening 24 serves to ensure that the clamping sleeve 23 with a defined Spring force is pressed into the bore 22 in the magnet pot 18. The slit-shaped Opening 24 allows the clamping sleeve 23 with a biasing force in the bore 22 is used. For this reason, when mounting the clamping sleeve 23 no Pressing forces are exerted on the magnet pot 18, as in a closed sleeve the case would be. Due to the high required pressing forces with closed sleeves they can blow up the magnet pot 18. This is achieved by the use of the invention Clamping sleeve 23 with the gap-shaped opening 24 avoided.

Between the upper housing part 15 and the magnet pot 18 is an adjusting ring 25, over the thickness of the stroke of the valve needle 3 is adjusted.

The clamping sleeve 23 is supported with an end face against the adjusting ring 25. To this Way are the impact forces when you hit the valve needle 3 during the opening process acting on the clamping sleeve 23, transmitted to the adjusting ring 25.

In order to avoid that the clamping sleeve 23 is magnetized by the coil 19 and thus may affect the switching operation of the valve needle 3, the clamping sleeve 23 is preferably made of a non-magnetizable material. Also, the material of the clamping sleeve 23 the impact forces acting on the clamping sleeve 23 when the valve needle 3 is hit, transferred to the adjustment ring 25 and may not be damaged by these impact forces. For this reason, a carbon steel is preferably used as the material for the clamping sleeve 23 elected. Other suitable materials for the clamping sleeve are, for example, stainless Steels.

Reference numeral 26 denotes a second electrical connection in the control valve 1. Via the second electrical connection 26, for example, another valve in Fuel injector to be powered. The power supply of the fuel injector via contact 27.

FIG. 2 shows the detail Z from FIG. 1.

FIG. 2 shows that the stop diameter 28 of the end face 14 of the valve needle head 11 is smaller than the outer diameter 29 of the clamping sleeve 23. In this way it is ensured that the valve needle 3 abuts exclusively against the clamping sleeve 23 and not against the magnetic pot 18, since a striking against the magnet pot 18 to a Damage could cause the same.

When opening the valve needle 3, the stroke by striking the end face 14 of the Valve needle head 11 is limited to the clamping sleeve 23. When closing, the stroke of the Valve needle 3 thereby limited that the valve needle 3 in the not shown in Figure 2 Flat seat 7 is provided. The stroke of the valve needle 3 is shown by reference numeral 30.

In order to avoid that the armature 21 is glued to the magnet pot 18 with the valve open, a residual air gap 31 is provided. The gluing of the armature 21 to the magnet pot 18 results from the fact that due to the small size of the fuel injector all Surfaces have a very low roughness. A thin fuel film between For this reason, two surfaces are adhesive.

The setting of the residual air gap 31 takes place in accordance with the invention Fuel injector such that the valve needle head 11 by the height of the residual air gap 31st protrudes from the armature 21.

FIG. 3 shows a plan view of a magnet pot with a clamping sleeve accommodated therein.

The plan view of the magnet pot 18 can be seen that in these at least one Bore 32 is received, which opens into an annular groove 33 for receiving the coil 19. In the embodiment shown in Figure 3, two holes 32 in the magnet pot 18 recorded. The bores 32 serve to receive the electrical connection 20, with which the coil 19, through which the magnetic field is generated, is supplied to and Receiving the second electrical connection 26, for example, for power supply a second valve is used in the fuel injector. Centered in the preferred formed with a circular cross-section magnetic pot 18, the bore 22 is received. In the bore 22, the clamping sleeve 23 is arranged, which with a spring force against the wall of the bore 22 is pressed. For applying the spring force is in the Clamping sleeve 23, the gap-shaped opening 24, extending between the end faces of the clamping sleeve 23 extends, trained. The spring force is applied by the clamping sleeve 23 is compressed, whereby the width of the slit-shaped opening 24 is reduced and the diameter of the clamping sleeve 23 is reduced. The pretensioned clamping sleeve 23 is inserted into the bore 22. In the bore 22, the bias of the Tensioning sleeve 23 is taken so that it opens into its original shape. This opening is interrupted by the wall of the bore 22, so that the clamping sleeve 23 with a residual spring force against the wall of the bore 22 is pressed. The remaining spring force is so great that a shaking stress and the mass of the clamping sleeve 23 does not lead to a release of the clamping sleeve 23. In this way, the clamping sleeve 23rd fixed due to the spring force in the bore 22 of the magnet pot 18 (press fit).

FIG. 4 shows a magnetic pot with a clamping sleeve received therein before the final one Surface treatment.

In the magnet pot 18 is the annular groove 33 for receiving the coil 19. Die Ring groove 33 is connected to the bores 32, so that the coil 9 in the annular groove 33 via the bore 32 can be supplied with power.

Figure 4 can be seen that the clamping sleeve 23 to form a projection 35 protrudes from the magnet pot 13. This shows the step in the assembly, though the clamping sleeve 23 is already inserted in the magnet pot 18, but the end face 34 of the Magnet pot 18 is not yet ground flat.

In contrast, FIG. 5 shows the magnet pot 18 with inserted clamping sleeve 23 and surface ground End face 34 of the magnet pot 18 and end face 36 of the clamping sleeve 23. Der Advantage of the assembly process, in which first the clamping sleeve 23 in the magnet pot 18th is used and then the magnetic pot 18 with inserted therein clamping sleeve 23rd brought to a common height 37, lies in the fact that the components are not paired Need to become. That means, it does not have to be taken care that the height 37 of the Magnet pot 8 and the length of the clamping sleeve 23 match exactly. This leads to, that the clamping sleeve 23 during the manufacturing process not multiple times in the magnet pot 18 must be used and removed for post-processing out of this, because the processing is done together. As a result, a cost-effective installation is possible. Due to the common grinding of magnet pot 18 and clamping sleeve 23 is an exact plane surface 34, 36 achieved.

FIGS. 6.1, 6.2 and 6.3 show various embodiments of the invention between the End-side extending gap-shaped openings shown. Thus, Figure 6.1 shows a in axial direction between the end faces extending gap-shaped opening 24 in the Clamping sleeve 23.

In Figure 6.2 is a spiral around the clamping sleeve 23 running around gap-shaped opening 24 shown. In this case, the part of the gap-shaped opening 24, which is on the plane of the drawing protruding side of the clamping sleeve 23 is located, with dashed lines dargstellt. In addition to the illustrated here Austührungsvariante once with the clamping sleeve 23 circumferential gap-shaped opening 24, the gap-shaped opening 24 can also in the Form a spiral around the clamping sleeve 23 several times.

Another embodiment for the gap-shaped opening 24 is dargstellt in Figure 6.3. Here, the gap-shaped opening 24 extends arcuately on the clamping sleeve 23rd

In addition to the shapes shown in Figures 6.1, 6.2 and 6.3, in which the gap-shaped Opening 24 may extend between the end faces of the clamping sleeve 23, is also everyone further course known in the art possible. In the formation of the slit-shaped Opening 24 is merely to make sure that this between the end faces of the Clamping sleeve 23 extends.

In order to avoid that the valve needle 3 canted when striking the clamping sleeve 23, the width of the gap-shaped opening 24 is maximum in a preferred embodiment 25% of the circumference of the clamping sleeve 23.

Another possibility, a tilting of the valve needle 3 when hitting the clamping sleeve 23 is shown in FIG.

Here is against the clamping sleeve 23 in the bore 22 in the magnet pot 18, a second clamping sleeve 38 braced. The assembly of the second clamping sleeve 38 is analogous to the assembly the clamping sleeve 23. To avoid that the valve needle 3 canted when hitting and to provide a uniform stop surface is the gap-shaped Opening 39 of the second clamping sleeve 38 to the gap-shaped opening 24 of the clamping sleeve 23rd added. This ensures that the end face 14 of the valve needle head 11th strikes over the entire circumference of the clamping sleeves 23, 38.

It is also possible that more than two clamping sleeves 23, 38 are used. In a preferred embodiment, the gap-shaped openings 24, 39 of the clamping sleeves 23, 38 offset when using more than two clamping sleeves so that the gap-shaped opening of each clamping sleeve at a different position, on the circumference located.

LIST OF REFERENCE NUMBERS

1

control valve

2

valve body

3

valve needle

4

stop plate

5

first valve chamber

6

End face of the stop plate. 4

7

flat seat

8th

second valve chamber

9

guide pin

10

drilling

11

Valve needle head

12

spigot

13

closing element

14

End face of the valve needle head 11

15

Upper housing part

16

End face of the upper housing part 15th

17

locknut

18

magnet pot

19

Kitchen sink

20

electrical connection

21

anchor

22

Hole in the magnet pot 18

23

clamping sleeve

24

slit-shaped opening

25

adjustment

26

second electrical connection

27

Contact

28

Stop diameter

29

Outer diameter of the clamping sleeve 23

30

stroke

31

Residual air gap

32

drilling

33

ring groove

34

End face of the magnet pot 18

35

head Start

36

Front side of the clamping sleeve 23

37

Height of the magnet pot 18

38

second clamping sleeve

39

slit-shaped opening of the second Clamping sleeve 38

Claims (11)

Fuel injector for internal combustion engines with a control valve (1) with an electromagnetically operable valve needle (3), wherein a coil (19) in a magnetic pot made of magnetizable material pot (18) is accommodated, characterized in that in the magnet pot (18) at least one clamping sleeve (23) is received with a running between the end faces gap-shaped opening (24). Fuel injector according to claim 1, characterized in that the clamping sleeve (23) is clamped by spring force against the wall of a bore (22) in the magnet pot (18). Fuel injector according to claim 1 or 2, characterized in that the clamping sleeve (23) is made of a non-magnetizable material. Fuel injector according to one of claims 1 to 3, characterized in that the clamping sleeve (23) is not deformed by the striking of the valve needle (3) when opening the valve. Fuel injector according to one or more of claims 1 to 4, characterized in that the clamping sleeve (23) encloses a closing element (13). Fuel injector according to one or more of claims 1 to 5, characterized in that the width of the gap-shaped opening (24) is at most 25% of the sleeve circumference of the clamping sleeve (23). Fuel injector according to one or more of claims 1 to 6, characterized in that the length of the clamping sleeve (23) of the height (37) of the magnet pot (18) corresponds, so that end faces (34, 36) of the clamping sleeve (23) and magnet pot ( 18) form a smooth surface. Fuel injector according to one or more of claims 1 to 7, characterized in that the outer diameter (29) of the clamping sleeve (23) is at least as large as the stop diameter (28) of the end face (14) of the valve needle head (11). Fuel injector according to one or more of claims 1 to 8, characterized in that in the magnet pot (18) at least two clamping sleeves (23, 38) are received, the gap-shaped openings (24, 39) are arranged at different radial positions. A method for producing a fuel injector according to one or more of claims 1 to 9, characterized in that the clamping sleeve (23) is first pressed into the magnet pot (18) under spring preload and then the magnet pot (18) together with the clamping sleeve (23) on a Height (37) is ground to obtain flat faces. A method according to claim 10, characterized in that the force with which the clamping sleeve is pressed into the magnet pot, is dimensioned so that for releasing the clamping sleeve an extrusion force in the range of 100 to 500 N is required.

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