EP1744054B1 - Active armature lift setting of fuel injectors - Google Patents

Abstract

The method involves subjecting of the load on the armature pin in the closing position of the closing element (16), whereby the armature pin (21) causes the push, thereby changing the armature stroke. The fuel injector (1) comprises a solenoid valve with an integrated fuel recirculation (11) and an injector body with a valve piece (4).

Description

The invention relates to a method for adjusting the armature stroke in a fuel injector of internal combustion engines such as in the documents EP 1 429 350 . WO 95/30830 or DE 2 936 425 shown. To supply combustion chambers of self-igniting internal combustion engines with fuel, stroke-controlled injection systems can be used, with rapidly switching solenoid valves being used to control an injection valve of an electrically controlled fuel injection device with injection valve member. The injection valve member of the fuel injection device is thereby loaded by a prevailing in a control chamber pressure in the closing direction. To initiate the injection of the excited magnet of the solenoid valve leads to a pressure relief of the control chamber, whereupon the injection valve member is lifted by the voltage applied to the opposite side of the high pressure of their seat.

State of the art

DE 196 50 865 A1 describes a solenoid valve for controlling the fuel pressure in a control chamber of an injection valve, for example, a common rail injection system. About the fuel pressure in the control chamber, a stroke movement of a valve piston is controlled, with which an injection port of the injection valve is opened or closed. The solenoid valve comprises an electromagnet, a movable armature and an injection valve member which is moved with the armature and acted upon by a valve closing spring in the closing direction and which cooperates with a valve seat of the solenoid valve and thus controls the fuel drain from the control chamber. The injection valve member includes a closure member and a closure member guide body partially enclosing the closure member. The movable armature is expediently designed in several parts so as to reduce the moving mass of the assembly armature injection valve member and thus the bouncing of the injection valve member at its seat and a ringing of the armature causing kinetic energy. The two-piece armature includes an anchor bolt and an armature plate slidably received on the armature bolt against the force of a return spring in the closing direction of the injection valve member under the action of its inertial mass.

The opening stroke of the injection valve member in a fuel injector, also referred to as anchor stroke, is decisive for the injected fuel quantity per unit time and is typically at values of 50 μm with a tolerance range of +/- 4 μm. According to the solution DE 196 50 865 A1 the opening stroke adjustment of the injection valve member takes place via shims. For this purpose, the individual dimensions of the components to be joined together of a fuel injector, which are relevant for the opening stroke, determined in a mechanical process and then selected according to the determined dimensions and tolerances from a wide range of panes, the correspondingly appropriate adjustment or spacer. For this purpose, the magnet of the solenoid valve is clamped and loaded with a defined hold-down force F1. With a hold-down force F2, the armature plate, including the armature pin, the valve spring and a valve spring adjustment disc is pressed against the magnet and determines a measure a, which represents the distance between the lower, the injection valve member facing end face of the anchor bolt and the contact surface of the adjusting of the solenoid valve. The measuring of an injector or holding body takes place in which a hold-down force F4 acts on the clamped injector body and the injection valve member is loaded with a hold-down force F5. The difference measure b between the contact surface of the injection valve member with the anchor bolt and the bearing surface of the adjusting washer on the injector body is determined. This determines the thickness of the shim from the difference of the dimension a to measure b plus the set value of the opening stroke, referred to as AH _soll .

The solenoid valve, which is open at the top for a fuel return, is then screwed together with the appropriately dimensioned adjustment dial with the actual injector body. In this screwed or clamped state, the opening stroke is measured with high precision by means of laser distance measurement by means of the fuel return.

For use in high-pressure injection system injectors tolerances in the micrometer range tolerable at most tolerances to ensure a reproducible injection valve behavior for the armature stroke. Due to the permitted only very small tolerance deviations, the armature stroke is not always within the tolerance range according to a procedure as described above, which is largely determined by the manufacturing tolerances of the components of the injection valve. Accordingly, the individual components of an injection valve are currently being measured and / or classified outside and within the production lines by complex measuring methods.

In order to subsequently achieve an adjustment of the armature stroke within the narrow tolerance range, the injection valve must be completely disassembled and the choice of a shim be reset with a different dimensioning of the armature stroke. If necessary, this process is repeated several times until there is an acceptable tolerance setting of the armature stroke in the injection valve. This often iterative approach is extremely time consuming and therefore costly. In addition, the disassembly and selection of the correct shim requires a great deal of experience on the part of the staff to minimize rework. Overall, the currently practiced procedure is considered to be extremely unsatisfactory and is unsuitable for future injector generations, since they require even lower tolerance values.

Advantages of the invention

The object of the present invention is to provide a simple method with which an armature stroke adjustment in an injection valve with a fuel return within a solenoid valve is largely independent of individual tolerances of the components and can be actively set in the screwed state of the solenoid valve with an injector body. In particular, armature stroke tolerances required for future injector generations are to be made possible without high cost, i. without reducing the manufacturing tolerances of all the individual components of the injector, which would require new manufacturing processes, new equipment, more accurate measurement techniques for manufacturing tolerance monitoring.

The method according to the invention allows the armature stroke adjustment in the screwed state of the injection valve. In this case, a direct influence is taken on a measure b, which represents the distance between an upper contact surface of an injection valve member, which comprises a closing element guide body and a closing element, and the bearing surface of the adjusting washer on the injector body. With the proposed method, a plastic deformation is preferably introduced exclusively into the closing element guide body by an applied embossing force such that the decisive for the armature stroke dimension b changes, whereby a smaller, standard armature stroke is increased to the target value of the armature lift. In particular, embossing of the closing element into the closing element guide body is achieved by the applied embossing force.

In the screwed or clamped state of the solenoid valve with integrated fuel return to the injector body a suitable die is introduced by the fuel return and acts on the injection valve member opposite end face of the anchor bolt with a defined embossing force. As a result of this load, the embossing force acts on the anchor bolt, on the closure member guide body, on the closure member which fits into its seat on the closure member guide body and optionally is impressed in his valve seat on a valve piece of the injector body accordingly. As a result, the dimension b changes, and thus over the previously mentioned context, the armature stroke AH _soll .

Thus, an active setting of a desired armature stroke, associated with a narrow tolerance range, in the assembled state of the injection valve is possible, which is largely decoupled from manufacturing variations of the individual components of the injection valve. The accuracy of the armature stroke adjustment is largely independent of the tolerances of the components. The inventive method itself is no longer based on expensive measuring methods for testing the injection valve components, so that they can be reduced if not even eliminated. The implementation of the assembly of the injection valve, i. screwing the solenoid valve and injector body no longer affects the armature stroke achieved and its tolerance values. Iterative methods for calculating the dimensioning of the shim omitted and the classification of the shim reduces in effort. The method provides a cost effective and relatively simple solution to the exact adjustment of the armature stroke.

The stamp used for the inventive method is designed so that it can be safely and easily introduced into the fuel return of the solenoid valve without damaging this during the stamping process. The material used for the die has higher hardness and strength values than the corresponding sizes of material from which the anchor bolt is made. The closing element, which is preferably designed as a ball, consists in particular of passenger car injection valves made of silicon nitride, which ensures that deform during the embossing process only the closing element guide body and the valve seat of the valve piece according to the embossing.

However, the deformation of the valve seat on the valve piece can influence the flow conditions in the valve opening area. To counteract this, the closing element guide body is modified such that the embossing force applied by the embossing stamp almost exclusively leads to a plastic deformation on the closing element guide body, while the valve seat remains unchanged on the valve piece.

drawing

Reference to the drawing, the Erfmdung is explained in more detail below.

Figur 1

einen Schnitt durch einen Kraftstoffinjektor mit einem Magnetventil mit einer integrierten Kraftstoffrückführung und einer Einstellscheibe zur Festlegung eines Ankerhubs gemäß des Standes der Technik;

Figur 2

einen Schnitt durch einen Kraftstoffinjektor mit einem Magnetventil und den zur Klassierung der Einstellscheibe relevanten Maßen, gemäß des Standes der Technik;

Figur 3

einen Schnitt durch einen Kraftstoffinjektor mit einem Magnetventil und einem eingeführten Prägestempel während einer erfindungsgemäßen aktiven Ankerhubeinstellung;

Figur 4

einen erfindungsgemäßen Prägestempel;

Figur 5

einen Schnitt durch einen erfindungsgemäßen Schließelementführungskörper.

It shows:

FIG. 1

a section through a fuel injector with a solenoid valve with an integrated fuel return and a shim for determining an armature stroke according to the prior art;

FIG. 2

a section through a fuel injector with a solenoid valve and the relevant for classifying the dial dimensions according to the prior art;

FIG. 3

a section through a fuel injector with a solenoid valve and an inserted die during an active Ankerhubeinstellung invention;

FIG. 4

an embossing die according to the invention;

FIG. 5

a section through a closing element guide body according to the invention.

embodiments

FIG. 1 shows a section through a fuel injector with a solenoid valve with an integrated fuel return, wherein an armature stroke is set via a shim, according to the prior art.

The in FIG. 1 shown fuel injector 1 comprises an injector body 2, in which in a cylinder bore 3, which is introduced into a valve member 4, an axially movable injection valve member 5 is movably guided. The injection valve member 5 is acted upon at one end face via the pressure prevailing in a control chamber 6 pressure. The filling of the control chamber 6 via an inlet throttle 7. coaxial with the injection valve member 5 branches off from the control chamber 6 in the valve piece 4 extending discharge channel 8 from which contains an outlet throttle 9 and opens into a discharge chamber 10, in a manner not shown with a fuel return 11 of the fuel injector 1 is connected.

The relief channel 8 opens into a conically countersunk region 12 on the outer end side of the valve piece 4. The valve piece 4 is clamped in a flange 13 fixed by a screw 14 with the injector 2. In the region of the outlet of the discharge channel 8 at the conically countersunk portion 12, a valve seat 15 is formed, with which a closing element 16 of a solenoid valve actuating the injection valve 17 cooperates. That in the FIG. 1 Spherically shaped closing element 16 is partially enclosed by a closing element guiding body 18 adapted to the contour of the closing element 16. The closing element guide body 18 bears against an end face 19 of an anchor bolt 21, which forms an anchor plate 22 a multi-part armature 20. This cooperates with an electromagnet 23 of the solenoid valve 17. The armature plate 22 is mounted dynamically displaceable on the anchor bolt 21 under the action of its inertial mass against the biasing force of a return spring 24 and is pressed by the return spring 24 against a stop 25 on the anchor bolt 21. The return spring 24 is supported on the housing side against a contact surface 26 of the anchor bolt 21 leading screw piece 14, which is clamped in the injector body 2. Also on the contact surface 26 is a shim 27, which limits the path of the armature plate 22 in the closing direction. The anchor bolt 21 and the closing element 16 coupled with it, as well as the anchor plate 22 are constantly acted upon by a valve spring 28 which is fixed to the housing and bears against a valve spring adjustment disk 29 in the closing direction, so that the closing element 16 is normally in the closed position on the valve seat 15. Upon energization of the electromagnet 23, the armature plate 22 is attracted by the electromagnet 23 and thus the discharge channel 8 is opened to the control chamber 6 out.

Between the solenoid valve 17 and the injector body 2, a shim 30 of a thickness s determined in a measuring method is inserted, which defines an armature stroke of the closing element 16 in the clamped state of the magnetic valve 17 and injector body 2.

In FIG. 2 the relevant dimensions for determining the armature stroke of the closing element 16 are illustrated. A measure a represents the situation when the electromagnet 23 is energized and gives the distance between the end face 19 of the anchor bolt 21, wherein the position of the end face 19 is designated 19 'in the energized state of the electromagnet 23 to the contact surface 31 on the solenoid valve 17 for classifying dial 30 in the open state of the injection valve member 5 again. A measure b is determined on the injector body 2 in a state that simulates the closed position of the injection valve member 5. The dimension b represents the distance between an end face 32 of the closing member guide body 18, which comes to rest with the end face 19 of the anchor bolt 21, to a bearing surface 33 on the injector body 2 for the shim 30 to be inserted. The thickness s of the shim 30 results from the difference between the dimension a and the dimension b plus the set value of the armature stroke AH _Soll , which in FIG. 2 designated by reference numeral 34. After the individually determined determination of the dimensions a and b and taking into account the target value of the armature stroke AH _Soll , the shim 30 with the thickness s can now be placed on the support surface 33 and solenoid valve 17 and injector 2 are braced against each other. By means of a laser distance measurement by the fuel return 11 now the fixed armature stroke of the closing element 16 is measured. The tolerance of the armature stroke is particularly dependent on the manufacturing tolerances of the individual components of the fuel injector 1 and can not be changed in the present fuel injector 1 without a complete disassembly of the fuel injector 1.

In FIG. 3 the process of the invention is illustrated.

In the fuel injector 1, an embossing punch 35 is introduced by the integrated fuel return 11, which is adapted in its configuration of the geometry of the fuel return 11. The die 35, shown in FIG FIG. 4 , which is preferably made of a material which has a higher hardness / strength than that of the anchor bolt 21, comprises regions of different diameters, which give a stepped outer contour. In particular, an end face 36 of the embossing punch 35 bears against a contact surface 37 of the anchor bolt 21 during the embossing process, whereby the embossing force introduced into the embossing punch 35 from above is transmitted via the contact surface 37 in the anchor bolt 21, via the closing element guide body 18, to the closing element 16.

Given a suitable choice of material of die 35, anchor bolt 21 and closing element 16, the applied stamping force leads to deformation of the closing element guide body 18, in particular on a contact surface 38 of the closing element guide body 18 and for deformation of the valve piece 4, in particular in the tapered region 12 of the valve seat 15 Valve seat 15 resulting from the embossing change in shape can affect the flow conditions in the opening region of the discharge channel 8 on the valve seat 15 have. Plastic deformation is therefore desired only on the closure element guide body 18. In order to avoid the often undesirable effect on the flow conditions in the opening area, a correspondingly modified design of the contact surface 38 on the closing element guide body 18 can be formed, as shown in FIG FIG. 5 is clarified. The contact surface 38 on the closure element guide body 18 for receiving the closure element 16 has a contour which provides exposed regions 39 which, due to the plastic deformation introduced during the embossing process, approximate to the shape of the closure element 16.

The successful implementation of the method according to the invention sets in tensioned fuel injectors 1 an armature stroke AH _is predicted, which is smaller than the desired armature stroke AH _Soll . The exact setting of the armature stroke AH _Soll with small tolerance can be done by embossing. Here, a distinction is made between a method which represents an achieved embossing depth as a function of the applied embossing force and a method which represents the embossing depth achieved as a function of the path of the embossing punch.

In the method according to the invention, in which the embossing depth is a function of the stamping force, the prevailing armature stroke AH _Ist in the strained fuel injector 1, which results after the assembly of the individual components, is first determined. The embossing punch 35 is introduced into the fuel return 11 such that the end face 36 of the embossing punch 35 comes to lie against the contact surface 37 of the anchor bolt 21. The embossing punch 35 is acted upon by a first embossing force with direction of action toward the anchor bolt 21, which leads to a deformation of the contact surface 38 on the closing member guide body 18 by impressing the closing element 16. After this first embossing process with a first embossing force, the now prevailing armature stroke AH _is again measured. Gives way to the armature stroke AH determined _actual or from the target value of the armature stroke AH from _target, then in a further embossing or steps can be changed with decreasing embossing forces of the armature travel until the desired armature stroke is achieved AH _target with the desired tolerance. Here prevailing stamping forces can be in a range of a few kN, whereby embossing depths up to a few microns can be achieved.

In particular, care must be taken in the choice of the applied embossing forces that the closing element 16 is not damaged. Separately performed tests have shown that the breaking point of a spherical closure member 16 is above the specified range of forces and beyond a stabilizing effect by the partial enclosure of the closing member 16 is achieved by the closing member guide body 18.

An alternative approach is based on the functional relationship between the achieved embossing depth and the way the die 35 passes. For this purpose, the prevailing armature stroke AH _{Ist is determined} in the fuel injector 1. In a deviation of the prevailing armature lift AH _is from the desired armature travel AH _If the imported into the Kratstoftrückführung 11 stamper 35 is applied with a Vorprägekraft which causes in particular on the closing element guide body 18 no plastic deformation but only results in a material reduction of the contact surface 38th At constant pre-compression force of the die 35 is moved by a certain distance in the embossing direction. Subsequently, the prevailing armature stroke AH _{Ist is} determined and compared with the target value of the armature lift AH _Soll . Depending on this, this process can be repeated until the desired result is achieved.

With the proposed method, two approaches being possible, an active armature stroke adjustment can be achieved which avoids disassembly of the fuel injector and thus presents itself as extremely inexpensive and easy to handle. By embossing according to the invention not only the armature stroke can be adjusted, but also the narrowest tolerance ranges of the armature stroke are maintained, without causing high costs at the same time. Since this procedure is performed on the finished fuel injector, drastically reduces the amount of waste fuel injectors, which have previously proved unsuitable for further use, since their anchor strokes were outside the tolerance range. Moreover, the method according to the invention proves to be particularly advantageous with regard to the constancy of the injection quantity of fuel, since an armature lifting drift, which arises in the first operating times of the fuel injector, is anticipated by the stamping in of the closing element in particular.

LIST OF REFERENCE NUMBERS

1

fuel injector

2

injector

3

bore

4

valve piece

5

Injection valve member

6

control room

7

inlet throttle

8th

relief channel

9

outlet throttle

10

relief chamber

11

Fuel return

12

conically countersunk area

13

flange

14

screw piece

15

valve seat

16

closing element

17

magnetic valve

18

Closing element guide body

19

face

19 '

Position of the end face 19 in the open state

20

multi-part anchor

21

anchor bolts

22

anchor plate

23

electromagnet

24

return spring

25

attack

26

contact surface

27

Focusing

28

valve spring

29

Ventilfederkrafteinstellscheibe

30

Focusing

31

contact surface

32

face

32 '

Position of the face in the closed state

33

bearing surface

34

AH _target setpoint of the opening

35

dies

36

End face stamping

37

Contact surface Anchor bolt

38

contact area

39

areas

s

Thick shim

a

Distance in solenoid valve

b

Distance in injector body

AH

armature stroke

Claims (9)

1. Method for setting the armature lift of a multi-component armature (20) in a fuel injector (1) which comprises a solenoid valve (17) with an integrated fuel return line (11) and an injector body (2) with a valve piece (4), the multi-component armature (20) having an armature bolt (21) and an armature plate (22) which can be displaced on the armature bolt (21), and is connected to a closing element guide body (18) which partially encloses a closing element (16), characterized in that in a closed position of the closing element (16) the armature bolt (21) is subjected to a force which brings about plastic deformation in such a way that the armature lift is changed.
2. Method according to Claim 1, characterized in that the plastic deformation is brought about on the closing element guide body (18).
3. Method according to Claim 1, characterized in that the plastic deformation is brought about at a contact face (38) between the closing element guide body (18) and the closing element (16).
4. Method according to Claim 1, characterized in that the plastic deformation is brought about on an end face (19) of the closing element guide body (18).
5. Method according to one of Claims 1 to 4, characterized in that a stamping die (35) is introduced through the fuel return line (11) of the fuel injector (1) by means of which the armature bolt (21) is subjected to a force.
6. Method according to one of Claims 1 to 5, characterized in that the stamping die (35) is fabricated from a material which has a higher degree of hardness and strength than the material of the armature bolt (21).
7. Method according to one of Claims 1 to 6, characterized in that the setting of the armature lift of the multi-component armature (20) comprises the following steps:

   a) measurement of the prevailing armature lift (AH_act) of the multi-component armature (20) of the fuel injector (1);

   b) subjection of the stamping die (35) to a force which leads to plastic deformation on the closing element guide body (18) and/or the valve piece (4);

   c) measurement of the changed armature lift (AH_act) of the multi-component armature (20);

   d) repetition of steps a) to c) until the prevailing armature lift (AH_act) is in a predefined tolerance range of the armature lift (AH_setp).
8. Method according to one of Claims 1 to 6, characterized in that the setting of the armature lift of the multi-component armature (20) comprises the following steps:

   a) measurement of the prevailing armature lift (AH_act) of the multi-component armature (20) of the fuel injector (1) ;

   b) subjection of the stamping die (35) to a force which does not bring about any plastic deformation;

   c) advancing of the stamping die (35) with constant application of force,

   d) measurement of the changed armature lift (AH_act) of the multi-component armature (20);

   e) repetition of steps a) to d) until the prevailing armature lift (AH_act) is in a predefined tolerance range of the armature lift (AH_setp).
9. Method according to one of Claims 1 to 8, characterized in that the closing element (16) is fabricated from silicon nitride.

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