EP1607620B1 - Fuel injector with clamping sleeve as a stop for a valve needle - Google Patents

Description

Technical area

For fuel supply of internal combustion engines fuel injection valves are often used today. In order to comply with emission limits and to reduce fuel consumption, it is necessary that the amount of fuel injected into each cylinder be accurately measured. For this extremely short opening and closing times of the injection valve are required. Furthermore, the valve needle must have the same stroke each time it is opened to ensure that the same amount of fuel is injected into the cylinder. This is realized by a stroke limitation.

State of the art

In the fuel injectors available on the market limiting the stroke of the valve needle takes place in different ways.

Thus, the stroke limitation is realized, for example, by the use of a stop disc against which the valve needle abuts. In this case, the stop disc rests on the magnet pot, so that a direct impact of the valve needle is avoided on the magnet pot. The stroke required for the operation of the fuel injector and the residual air gap are adjusted by grinding in projections 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, the stroke and the residual air gap are adjusted by shims whose thickness is adapted to the stroke or the residual air gap.

The use of a hold-down with a sleeve-shaped stopper, which is surrounded by the magnetic pot, provides another way to realize the stroke limitation. Such a sleeve-shaped stop is off DE 102 49 161 B3 known. Here, the stroke is adjusted by a shim between the valve body and the hold-down and the residual air gap by grinding the sleeve designed as a stop on the appropriate length.

To avoid eddy currents in the magnet pot, which delay the switching process of the fuel injector, the magnet pot, as described in Bosch Research Info, 3/2001, made of a metal / polymer composite material. For this purpose, fine iron particles are coated with plastic, pressed and sintered into a workpiece. However, this material is 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 out, which can change the magnetic properties of the magnet pot. Also, the erupted particles can cause higher wear and thereby lead to failure of the fuel injector.

A fuel injection valve with a clamping sleeve having an axial slot for forming a bias is out DE 10109 411 A1 known. The clamping sleeve is braced as an abutment for a return spring of a valve needle in a tubular opening of a housing part.

Presentation of the invention

In order to prevent a striking of the valve needle to the magnet pot, is in the inventively designed fuel injector, which is controlled by a control valve with an electromagnetically actuated valve needle, the sleeve-shaped stop formed by a tensioned in the magnet pot clamping sleeve.

For assembly, the clamping sleeve is biased and inserted into a bore, which is preferably centered in the magnet pot. Due to the bias creates a spring force in the clamping sleeve, through which the clamping sleeve is pressed against the wall of the hole and so holds in the magnet pot. The spring force is dimensioned so that the clamping sleeve does not solve due to the shaking stress occurring during operation and the own mass.

So that the valve needle does not strike against the magnet pot when opening, the outer diameter of the clamping sleeve is greater than or equal to the diameter of the stop surface of the valve needle. The length of the clamping sleeve corresponds to the height of the magnet pot, so that the end faces of the clamping sleeve and magnet pot form a smooth surface. This is achieved by firstly pressing the at least one adapter sleeve into the magnet pot and subsequently grinding the end faces of the magnet cup with the clamping sleeve pressed into it. The residual air gap, which is required for the anchor of the valve needle does not stick to the magnetic pot, is achieved in that the stop surface of the valve needle protrudes from the armature of the valve needle by the amount of the residual air gap.

The required extrusion forces of the clamping sleeve from the magnet pot are preferably in the range of 100 to 500 N. The expression force is to be understood as the force which 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. A sleeve of magnetizable material has the disadvantage that even after completion of the current 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 delay.

Furthermore, the material from which the clamping sleeve is made, preferably not deformable by the impact of the valve needle. A plastic deformation of the clamping sleeve would cause the needle stroke increases with the service life of the fuel injector. An increase in the needle stroke, for example, lead to an increase in the injected fuel quantity and thus to a higher fuel consumption. A suitable material for the production of the clamping sleeve is for example carbon steel.

Due to the fact that the width of the gap-shaped opening extending between the end faces is at most 25% of the circumference of the sleeve, a kinking of the valve needle during striking is avoided and thus a precise opening is achieved. An annular abutment surface and thus a uniform abutment of the valve needle can be achieved in that at least two clamping sleeves are received in the magnet pot, whose gap-shaped openings extending between the end faces are arranged at different radial positions.

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 out FIG. 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

FIG. 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 bore in which a valve needle 3 is guided. On the one side of the injection valve, not shown here, a stop plate 4 connects to the valve body 2. On the side facing the stop plate 4, the bore in the valve body 2 opens into a first valve space 5. The first valve space 5 is delimited by an end face 6 of the stop plate 4. At the first valve chamber 5, a bore 10 in the stop plate 4 connects. 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 or closed in the stop plate 4.

To do that in FIG. 1 Not shown injection valve in the correct position to mount the control valve 1, a guide pin 9 is formed on the stop plate 4. For assembly, the guide pin 9 is inserted into a corresponding bore on the injection valve. In this way, it is ensured that, for example, the holes for channels passing through a plurality of components are aligned in the fully assembled fuel injector.

On the side facing away from the stop plate 4, the valve needle widens into a valve needle head 11. A guide pin 12 adjoins the valve needle head 11. The guide pin 12 is enclosed by a closing element 13 preferably designed as a spiral spring. 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 an upper housing part 15. By the guide pin 12 prevents the closure member 13 can slip on the end face 14 of the valve needle head 11. The guide pin 12 also prevents kinking of the closing element 13 during a lifting movement of the valve needle 3 out of the flat seat 7.

The valve body 2 and the upper housing part 15 are interconnected by a clamping nut 17.

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 having an annular groove formed in which a coil 19 is received. The coil 19 is powered by an electrical connection 20 with electricity. As soon as a voltage is applied to the coil 19, a magnetic field is formed around the coil 19. By this magnetic field, the material of the magnetic pot 18 is magnetized. As a result, an armature 21, which is made of magnetic material and encloses the valve pin head 11, is attracted by the magnet pot 18. In this way, the valve needle 3 moves in the direction of the magnet pot 18 and thus releases the flat seat 7. Here, the closing element 13 designed as a spiral spring is compressed. The closing element 13 is arranged within a bore 22 in the magnet pot 18, so that the magnet pot 18 encloses the closing element 13.

The material of the magnetic pot 18 is preferably a sintered metal or contains fine plastic-coated iron particles which have been pressed into a magnet pot 18. This avoids that arise in the magnet pot eddy currents that delay the switching process. This material is extremely brittle and therefore impact-sensitive. Therefore, it could come from the magnetic pot 18 by striking the valve needle 3 for breaking individual particles. This changes the magnetic properties. In addition, the broken particles can cause higher wear and thus lead to failure of the control valve 1. To intercept the shock load by striking the valve needle 3, a clamping sleeve 23 is received in the bore 22 in the magnet pot 18. The clamping sleeve 23 has a gap-shaped opening 24 extending between the end faces. 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 gap-shaped opening 24 allows the clamping sleeve 23 is inserted with a biasing force in the bore 22. For this reason, no pressing forces must be exerted on the magnetic pot 18 during assembly of the clamping sleeve 23, as would be the case with a closed sleeve. Due to the high required pressing forces with closed sleeves they can blow up the magnet pot 18. This is avoided by the use of the clamping sleeve 23 according to the invention with the gap-shaped opening 24.

Between the upper housing part 15 and the magnet pot 18 there 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. In this way, the impact forces acting on the clamping sleeve 23 during the striking of the valve needle 3 during the opening process are transmitted to the adjusting ring 25.

In order to avoid that the clamping sleeve 23 is magnetized by the coil 19 and thus can influence 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 hitting the valve needle, transmitted to the adjusting ring 25 and may not be damaged by these impact forces. For this reason, a carbon steel is preferably selected as the material for the clamping sleeve 23. 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. For example, another valve in the fuel injector can be supplied with power via the second electrical connection 26. The power supply of the fuel injector via contact 27th

FIG. 2 shows the detail Z out FIG. 1 ,

FIG. 2 can be seen 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. This ensures that the valve needle 3 abuts exclusively against the clamping sleeve 23 and not against the magnetic pot 18, as a striking against the Magnet pot 18 could lead to damage of the same.

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

In order to avoid that the armature 21 adheres to the magnet pot 18 when the valve is open, a residual air gap 31 is provided. The gluing of the armature 21 to the magnetic pot 18 results from the fact that due to the small component size of the fuel injector all surfaces have only a very small roughness. A thin film of fuel between two surfaces acts for this reason adhäsiv.

The setting of the residual air gap 31 takes place in the case of the inventively embodied fuel injector such that the valve needle head 11 protrudes from the armature 21 by the height of the residual air gap 31.

FIG. 3 shows a plan view of a magnetic pot with a clamping sleeve received therein.

The plan view of the magnet pot 18 can be seen that in this at least one bore 32 is received, which opens into an annular groove 33 for receiving the coil 19. At the in FIG. 3 illustrated embodiment, two bores 32 are received in the magnet pot 18. The bores 32 serve to receive the electrical connection 20, with which the coil 19, through which the magnetic field is generated, is supplied and for receiving the second electrical connection 26, which is used, for example, to supply power to a second valve in the fuel injector. Centered in the magnetic pot 18, which is preferably formed with a circular cross section, the bore 22 is accommodated. In the bore 22, the clamping sleeve 23 is arranged, which is pressed with a spring force against the wall of the bore 22. To apply the spring force is in the clamping sleeve 23, the gap-shaped opening 24 which extends between the end faces of the clamping sleeve 23 is formed. The spring force is applied by compressing the clamping sleeve 23, whereby the width of the gap-shaped opening 24 is reduced and the diameter of the clamping sleeve 23 is reduced. The biased clamping sleeve 23 is inserted into the bore 22. In the bore 22, the bias is taken from the clamping sleeve 23 so that it opens to its original shape. This opening is interrupted by the wall of the bore 22, so that the clamping sleeve 23 is pressed with a residual spring force against the wall of the bore 22. The remaining spring force is so great that a shaking stress and the mass of the clamping sleeve 23 do not lead to a release of the clamping sleeve 23. In this way, the clamping sleeve 23 is 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 surface treatment.

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

FIG. 4 can be seen that the clamping sleeve 23 protrudes from the magnet pot 13 with the formation of a projection 35. This shows the step in the assembly when the clamping sleeve 23 is already used in the magnet pot 18, but the end face 34 of the magnet pot 18 is not plan ground.

FIG. 5 In contrast, shows the magnetic pot 18 with inserted clamping sleeve 23 and flat ground end surface 34 of the magnet pot 18 and end face 36 of the clamping sleeve 23. The advantage of the assembly process, in which first the clamping sleeve 23 is inserted into the magnet pot 18 and then the magnet pot 18 with inserted therein clamping sleeve 23 is brought to a common height 37, is that the components do not have to be paired. That is, it must not be taken to ensure that the height 37 of the magnet pot 8 and the length of the clamping sleeve 23 match exactly. As a result, the clamping sleeve 23 does not have to be inserted several times into the magnet pot 18 during the manufacturing process and has to be removed from the magnet pot for subsequent processing since the machining takes place together. As a result, a cost-effective installation is possible. Due to the common grinding of magnetic pot 18 and clamping sleeve 23, a precisely planar surface 34, 36 is achieved.

In the Figures 6.1, 6.2 and 6.3 different embodiments of the running between the end faces gap-shaped openings are shown. So shows FIG. 6 , 1 a in the axial direction between the end faces extending gap-shaped opening 24 in the clamping sleeve 23rd

In FIG. 6 , 2 is a spiral around the clamping sleeve 23 running around gap-shaped opening 24 is shown. In this case, the part of the gap-shaped opening 24, which is located on the projecting into the plane of the side of the clamping sleeve 23, dargstellt with dashed lines. In addition to the embodiment shown here with a once around the clamping sleeve 23 circumferential gap-shaped opening 24, the gap-shaped opening 24 may rotate around the clamping sleeve 23 several times in the form of a spiral.

Another embodiment for the gap-shaped opening 24 is shown in FIG FIG. 6 , 3 dargstellt. Here, the gap-shaped opening 24 extends arcuately on the clamping sleeve 23rd

In addition to those in the Figures 6.1, 6.2 and 6.3 illustrated forms in which the gap-shaped opening 24 may extend between the end faces of the clamping sleeve 23, any further known to those skilled course is possible. In the formation of the gap-shaped opening 24 is only to ensure that it extends between the end faces of the clamping sleeve 23.

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

Another way to avoid tilting of the valve needle 3 when hitting the clamping sleeve 23 is in FIG. 7 shown.

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

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 from one another when using more than two clamping sleeves, that the gap-shaped opening of each clamping sleeve is located at a different position, on the circumference.

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 (8)

1. Fuel injector for internal combustion engines, having a control valve (1) with an electromagnetically actuable valve needle (3), a coil (19) being received in a magnet pot (18) manufactured from magnetizable material, at least one sleeve-shaped stop for limiting the stroke of the valve needle (3) being arranged in the magnet pot (18), and the valve needle (3) having a valve-needle head (11) which is surrounded by an armature (21), characterized in that the sleeve-shaped stop is formed by at least one tension sleeve (23) with a gap-shaped orifice (24) running between the end faces, which tension sleeve is braced by spring force against the wall of a bore (22) in the magnet pot (18), in that the length of the tension sleeve (23) corresponds to the height (37) of the magnet pot (18), so that end faces (34, 36) of the tension sleeve (23) and of the magnet pot (18) form a smooth surface, and in that the outside diameter (29) of the tension sleeve (23) is at least as large as the stop diameter (28) of the end face (14) of the valve-needle head (11).
2. Fuel injector according to Claim 1, characterized in that the tension sleeve (23) is manufactured from a non-magnetizable material.
3. Fuel injector according to Claim 1 or 2, characterized in that the tension sleeve (23) is not deformed as a result of the impact of the valve needle (3) during the opening of the valve.
4. Fuel injector according to one or more of Claims 1 to 3, characterized in that the tension sleeve (23) surrounds a closing element (13).
5. Fuel injector according to one or more of Claims 1 to 4, characterized in that the width of the gap-shaped orifice (24) amounts to at most 25% of the sleeve circumference of the tension sleeve (23).
6. Fuel injector according to one or more of Claims 1 to 5, characterized in that the magnet pot (18) receives at least two tension sleeves (23, 38), the gap-shaped orifices (24, 39) of which are arranged in different radial positions.
7. Method for producing a fuel injector according to one or more of Claims 1 to 6, characterized in that the tension sleeve (23) is first pressed into the magnet pot (18) under spring prestress, and the magnet pot (18), together with the tension sleeve (23), is subsequently ground to one height (37) in order to obtain plane end faces.
8. Method according to Claim 7, characterized in that the force with which the tension sleeve is pressed into the magnet pot is dimensioned such that a press-out force in the range of 100 to 500 N is required in order to release the tension sleeve.

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