EP2499350B1 - Method of manufacturing a fuel injector - Google Patents

Description

State of the art

The invention relates to a method for producing a fuel injection valve according to the preamble of claim 1.

Such a method for producing a fuel injection valve (hereinafter also referred to in part as "injector") is already well known and is used in particular in fuel injection valves in so-called common-rail injection systems. Hub-controlled common-rail injectors whose nozzle needle is servo-operated are known. Piezo and solenoid valves are used as pressure actuators, with which the servo circuit is controlled. For fast closing of the valve needle is often installed a permanent low-pressure stage, which exerts a permanent, closing force on the valve needle. The disadvantage here, however, is the relatively high leakage that occurs between the high and the low pressure side. Leakage inevitably results in a higher pumping capacity required in the common rail injection system and thus in system efficiency. This situation becomes problematic especially at higher pressures.

For this reason, the latest injectors for highest injection pressures (meaning here pressures in the range of about 2000bar) are designed low leakage, by dispensing with the low pressure stage. Due to the absence of the low-pressure stage, however, only low closing forces are available for the valve needle. As a result, the response time between the control of the valve needle and the start of injection relatively low. The response time is mainly dependent on the stiffness of the valve needle. Precisely because it is small in an injector without low-pressure stage, even a slight change in the needle stiffness leads to a large shift in the start of injection and the amount of fuel injected. The stiffness of the valve needle depends on the diameter and length of the valve needle. If you want to form injectors of different lengths equal in terms of their response time, so must be performed for each pattern or each length of the injector a corresponding sidecut or diameter variation of the valve needle. In this way, the stiffness of the valve needles can be adjusted for all injectors. However, this results in relatively high set-up times. Ideal would be a pure variation of the needle length, while the needle diameter is the same for all injector lengths. However, this is not possible due to the resulting differences in the stiffness of the valve needles.

From the US 6 213 098 B1 It is known to adjust the volume of the control chamber to produce the desired dynamics in the manufacture of a fuel injection valve.

Disclosure of the invention

Based on the illustrated prior art, the invention has the object, a method for producing a fuel injection valve according to the preamble of claim 1 such that the response time at fuel valves of different length or different length of their valve needles is at least substantially constant. This object is achieved in a method for producing a fuel injection valve having the features of claim 1. The invention is based on the idea to compensate for the different mechanical stiffness due to different lengths of the valve needles by a variation of the "hydraulic stiffness" of the valve connected to the valve needle in operative connection control space. This is based on the knowledge that the larger the volume is formed in the control chamber, the greater the delay or the response time until the injection openings are opened. In other words, this means that a relatively short and thus stiff valve needle is thereby compensated by being connected to a control chamber in operative connection, which has a relatively large storage volume of fuel and vice versa.

Advantageous developments of the method according to the invention for producing a fuel injection valve are specified in the subclaims. All combinations of at least two features disclosed in the description, the claims and / or the figures fall within the scope of the invention.

According to the invention, it is provided that the valve needle consists of at least one arranged in the control chamber, standardized first portion which is connected on the side facing away from the control chamber with a second cylindrical portion and that the diameter of the second portion of the valve needle is varied, such that Shortening of the delay time increases the diameter of the valve needle and is reduced to an extension of the delay time of the diameter of the valve needle.

In this case, it is particularly advantageous to limit the number of possible different diameters of the valve needles if the diameter of the valve needle is varied in diameter steps and that fine adjustment of the delay time is achieved by adjusting the volume of the control chamber via a variation of the length of the second cylindrical section , It takes place hereby a combination of a valve needle with a certain diameter with a valve needle of a certain length, such that the in the control room protruding portion of the standardized first section forms a certain control volume.

Moreover, it is particularly advantageous if, taking into account the minimum and maximum possible volume of the control chamber and the available diameter stages of the valve needles that diameter of the valve needle is selected, which leads to a minimum volume of the control chamber. This means that always the valve needle is selected, which has the smallest diameter. The further adaptation of the delay time is thus carried out via an extension or shortening of the valve needle.

In addition, a particularly economic manufacturability of the fuel valves results when the second section of the valve needle is connected to a standardized third section on the side opposite the standardized first section.

The connection between at least the second section of the valve needle and the standardized first section and optionally between the second section of the valve needle and the third section is preferably carried out by laser welding. As a result, high-strength compounds can be produced relatively economically.

Fuel valves produced in accordance with the inventive method can be produced particularly economically with respect to their overall length if the injector housing of the fuel injection valve has a standardized upper part with the closing element, an actuating mechanism for the closing element and optionally the valve piece and a standardized lower part with a nozzle body, and that between the Upper part and the lower part a total length of the injector housing defining central part is arranged.

Further advantages of the method according to the invention for producing a fuel injection valve and the fuel valve will become apparent from the following description of preferred embodiments and from the drawings.

Fig. 1 und 2

erfindungsgemäße erste Kraftstoffeinspritzventile, bei denen deren Injektorgehäuse eine maximale bzw. eine minimale Baulänge aufweist, jeweils im Längsschnitt und

Fig. 3 und 4

zweite erfindungsgemäße Kraftstoffeinspritzventile, bei denen die Injektorgehäuse eine maximale bzw. eine minimale Gesamtlänge aufweisen, ebenfalls im Längsschnitt.

These show in:

Fig. 1 and 2

Inventive first fuel injectors, wherein the injector has a maximum or a minimum length, respectively in longitudinal section and

3 and 4

second fuel injection valves according to the invention, in which the injector have a maximum or a minimum overall length, also in longitudinal section.

Identical components or components with the same function are provided in the figures with the same reference numeral.

In the Fig. 1 a first fuel injection valve 10 is shown, as used in particular in so-called common-rail injection systems use. Here, the fuel injection valve 10 is connected via a supply line 1 with a fuel storage, a so-called rail 2, in connection. In the rail 2 is stored under high pressure, for example, a pressure of about 2000 bar, standing fuel. In this case, the rail 2 is connected to a high-pressure fuel pump 3, which sucks and compresses fuel from a fuel reservoir, in particular a fuel tank 4. Fuel not required by the fuel injection valve 10 is returned to the fuel tank 4 via a return line 5 under low pressure.

A fuel injection system 7 described so far has a separate fuel injection valve 10 for each cylinder of an internal combustion engine, all of which are connected to the rail 2.

The fuel injection valve 10 has a generally designated 11 injector housing. Here, the elongated injector housing 11 consists of three modules, a standardized upper part 12, a dependent on the length of the fuel injector 10, in particular annular, possibly formed with different diameters middle part 13 and a likewise standardized lower part 14. Between the upper part 12 and the middle part thirteenth a sealing ring 15 is inserted in a sealing groove, wherein the pressure-resistant connection between the central part 13 and the upper part 12, for example, by a circumferential laser welding or by a circumferential beading. In contrast, between the middle part 13 and the lower part 14 with the interposition of a sealing ring 17 by way of example a screw connection 18 is formed in order to connect the middle part 13 to the lower part 14 in a pressure-resistant manner.

In the upper part 12, a pressure-balanced solenoid valve 20 is used or arranged, which has a magnetic core 21 and arranged in the magnetic core 21 magnetic coil 22. The solenoid valve 20 also has a magnetic armature acting as a closing element 23, which is guided in an axially movable manner in a pin-shaped guide member 24. The guide member 24 is disposed in a through hole 25 of the magnetic core 21 and has a step 26, between which and the facing side of the armature 23, a compression spring 28 is supported. The compression spring 28 is in this case arranged in a spring chamber 29 which, like the region of the upper part 12 in which the magnetic core 21 is located, is connected at least indirectly to the return line 5 and thus to low pressure.

The armature 23 is pressed in the de-energized state of the solenoid 22 against a seat 30 of a valve member 32. Here, the valve member 32 is screwed into an upper portion of the central part 13 and in this case sits on a step 33 of the central part 13. In the longitudinal axis of the valve piece 32, a through hole 34 is arranged with a flow restrictor 35. The outflow throttle 35 is connected to a control chamber 37, which is formed as a blind hole 38 on the magnet armature 23 opposite side of the valve member 32. In the blind hole 38 projects on the Abströmdrossel 35 opposite, open end, a first guide portion 39 of a valve needle 40 into it.

The substantially cylindrically shaped valve needle 40 has, at its end opposite the valve piece 32, a second guide section 41, to which a valve tip 42 adjoins. By means of a compression spring 43, which is supported between a collar 44 of the valve needle 40 and the facing end face of the valve member 32, the valve tip 42 is pressed against a seat 46 of a nozzle body 47. The seat 46 defines a nozzle space 48, in FIG the at least one serving as a fuel outlet opening 49 through hole opens. The nozzle body 47 is in this case inserted into the lower part 14 of the injector housing 11.

The function of a fuel injection valve 10 described so far is already well known and is therefore briefly explained as follows: In the de-energized state of the solenoid valve 20, the armature 23 is pressed by the force of the compression spring 28 against the seat 30, so that the control chamber 37 is closed. Furthermore, the valve needle 40 is pressed by means of the compression spring 43 against the seat 46, so that the fuel outlet opening 49 is closed. When the solenoid valve 20 or the solenoid 22 is energized, the magnet armature 23 lifts off from the seat 30, so that passage from the high-pressure fuel control chamber 37 into an armature space 51 is created, which communicates with the return line 5. The outflow of the fuel from the control chamber 37 causes the valve needle 40 lifts from its seat 46, and fuel from the high pressure storage chamber 52 and the nozzle chamber 48 through the fuel outlet opening 49 flows out of the fuel injection valve 10 via the inlet line 1 and into the combustion chamber the internal combustion engine is discharged.

Due to its length L ₁ and its material and thus its modulus of elasticity and its cross-sectional area A, the valve needle 40 has a certain rigidity. In the de-energized state of the solenoid valve 20, the valve needle 40 is pressed against the seat 46, wherein an elastic deformation of the valve needle 40 due to the material properties described above and the geometry of the valve needle 40 sets. When energizing the solenoid coil 20 and the associated pressure reduction in the control chamber 37, the lifting of the valve needle 40 from the seat 46 takes place only when the pressure prevailing on the upper end surface 53 of the valve needle 40 pressure or the corresponding axial force is reduced to the valve needle At the same time it is mentioned that also the pressure reduction in the control chamber 37, ie the period between the lifting of the armature 23 from the seat 30 to the reduction of the axial force on the end face 53, takes a certain period of time, which depends on the size of the Volume of the control room 37 depends. The sum of the delays caused by the pressure reduction in the first place Control chamber 37 and the other with respect to the elastic deformation of the valve needle 40, referred to as delay time or drive time t.

In the Fig. 2 a fuel injection valve 10 a is shown, which differs from that in the Fig. 1 illustrated fuel injector 10 differs in that it has a total of a smaller overall length. According to the invention, the smaller length is achieved by reducing or shortening the central part 13, while the lower part 14 and the upper part 12 are each formed as standardized components, which are present both in the fuel injection valve 10 and the fuel injection valve 10a in an identical manner. At the same time, the other, not directly with the central part 13 and the valve needle 40 operatively connected components in an identical manner are present. Thus, the fuel injection valve 10a differs from the fuel injection valve 10 only in the length of the central part 13 and in the length of the valve needle 40a. Since the length L _{2 of} the valve needle 40a, as well as the length of the central portion 13 with respect to the fuel injection valve 10 is lower, the fuel injection valve 10a with respect to the valve needle 40a has a lower response time, (provided that the valve needle 40 and the valve needle 40a from the same Material and have the same cross-sectional area A), the length L _{2 of} the valve needle 40a with respect to the length L _{1 of} the valve needle 40 is lower. This would thus also lead overall to a shortened drive time t of the fuel injection valve 10a. In order to make the actuation times t of both the fuel injection valve 10 and the injection valve 10a the same, it is provided according to the invention that the part of the activation time t, which is influenced by the volume of the control chamber 37, is increased in the fuel injection valve 10a relative to the fuel injection valve 10. This is done by increasing the volume of the control chamber 37 such that the projecting into the control chamber 37 guide portion 39a of the valve needle 40a is reduced in its length. In other words, this means that the shortening of the drive time t due to the small length L _{2 of} the valve needle 40a is compensated by an extension of the proportion of the drive time t due to the increased volume of the control space 37.

In the Fig. 3 and 4 For example, a third fuel injection valve 60 and a fourth fuel injection valve 60a are shown. The fuel injection valves 60, 60a differ from the fuel injection valves 10, 10a through the use of a differently constructed valve needle 62, 62a. Here, the valve needles 62 and 62a are each formed in three parts. Each of the valve needles 62, 62a consists of a standardized, protruding into the control chamber 37 upper part 63 and a standardized lower part 64, which carries the second guide portion 41 and the valve tip 42. The upper part 63 and the lower part 64 are interconnected by means of a cylindrically shaped middle part 65, 65a. In this case, the laser welding is preferably used as connection technology between the middle part 65, 65a and the upper part 63 or between the middle part 65, 65a and the lower part 64.

How to make a synopsis of the Fig. 3 and 4 detects, the middle part 65 has a larger diameter D ₁ , as the central part 65a with the diameter D _2nd Thus, the central part 65 has a larger cross-sectional area A ₁ than the central part 65 a with the cross-sectional area A ₂ . While it is provided in the fuel injection valves 10 and 10a, to influence the driving time t exclusively by a variation of the volume of the control chamber 37, the driving time t in the fuel injection valves 60, 60a mainly by a variation of the diameter D or the cross-sectional area A of the central part 65, 65a influenced. In this case, it is advantageously provided that the different diameters D of the middle parts 65, 65a are present only in stages for reducing the variety of types, ie that only a limited number of diameters D is provided or are present in the production for mounting fuel injection valves 60, 60a , In this case, a coarse adjustment of the activation times t is effected via the variation or selection of the middle parts 65, 65a. In this case, it is provided that, should it be possible to realize a specific activation time t by means of two different diameters D, the smaller diameter D is always used. This has the consequence that (compared to the larger diameter D), the volume of the control chamber 37 is smaller, to compensate for the lower rigidity of the equipped with the relatively smaller diameter D middle part 65. The fine tuning with respect to the actuation time t takes place at the selected diameter D now by a corresponding reduction or reduction of the length of the central part 65, 65 a in such a way that the region of the upper part 63, which is located in the valve piece 32, projects somewhat less into the control chamber 37.

Wobei

• E(37) der Elastizitätsmodul des Kraftstoffs im Bereich des Steuerraums 37,
• A(37) die Querschnittsfläche A im Bereich des Steuerraums 37,
• E(65; 65a) der Elastizitätsmodul des Abschnitts 65; 65a,
• A(65; 65a) die Querschnittsfläche A im Bereich des Abschnitts 65; 65a bedeutet und wobei das Verhältnis ΔH / ΔL erfindungsgemäß zwischen 100 und 500 liegt.

Here, the ratio of the increase in the valve needle lift ΔH due to the increase in the volume of the control space 37 for shortening the needle stroke due to the shortening of the valve needle ΔL can be calculated by: $$\mathrm{AH}/\mathrm{.DELTA.L}=\left(\mathrm{e}\left(\mathrm{37}\right)\mathrm{x\; A}\left(\mathrm{37}\right)\right)/(\mathrm{<figure-callout\; id="65"\; label="e"\; filenames="imgf0003.png"\; state="\{\{state\}\}">e</figure-callout>}\left(\mathrm{65};\mathrm{65}\mathrm{a}\right)\mathrm{<figure-callout\; id="65"\; label="x\; A"\; filenames="imgf0003.png"\; state="\{\{state\}\}">x\; </figure-callout>}\left(\mathrm{A}\right)\left(\mathrm{}\left(\mathrm{65};\mathrm{65}\mathrm{a}\right)\right)$$

In which

• E (37) the modulus of elasticity of the fuel in the region of the control chamber 37,
• A (37) the cross-sectional area A in the area of the control chamber 37,
• E (65; 65a) is the modulus of elasticity of section 65; 65a,
• A (65; 65a) the cross-sectional area A in the region of the section 65; 65a and wherein the ratio ΔH / ΔL according to the invention is between 100 and 500.

The fuel injection valves 10, 10a and 60, 60a described so far can be modified or modified in a variety of ways. In particular, the magnet assembly or the solenoid valve 20 may be constructed differently or replaced by a piezo. It is also shown in addition that the design of the fuel injection valves 10, 10a, 60, 60a can take place so that the solenoid valve 20 can already be closed again before the injection begins or the through-bore 34 is released. In this way, variations between successive injections and Gegenruckabhängigkeiten can be reduced.

Claims (6)

1. Method for producing a fuel injection valve (10; 10a; 60; 60a), in which method a valve needle (40; 40a; 62; 62a) which closes off at least one fuel outlet orifice (49) is inserted into an injector housing (11), wherein the opposite end of the valve needle (40; 40a; 62; 62a) from the at least one fuel outlet orifice (49) is guided in a valve piece (32) which has a pressurized, fuel-filled control chamber (37), wherein the control chamber (37) can be closed off, on the side facing away from the valve needle (40; 40a; 62; 62a), by a closing element (23) which, when opened, forms a passage and which is connected at least indirectly to a fuel return line (5) at low pressure, wherein after the opening of the control chamber (37) by means of the closing element (23), fuel volume present in the control chamber (37) flows out through the passage, wherein the valve needle (40; 40a; 62; 62a) moves in the direction of the closing element (23), wherein the at least one fuel outlet orifice (49) is opened up, and wherein between the opening of the control chamber (37) and the opening of the at least one fuel outlet orifice (49) there is a delay time (t) owing to the size of the volume of the control chamber (37) and owing to the stiffness of the valve needle (40; 40a; 62; 62a) arising from the modulus of elasticity, the diameter (D) and the length (L) of the valve needle (40; 40a; 62; 62a),
   characterized
   in that the valve needle (62; 62a) is composed of at least a standardized first portion (63) arranged in the control chamber (37), which first portion is connected, on the side facing away from the control chamber (37), to a second cylindrical portion (65; 65a) of the valve needle (62; 62a), and in that the diameter (D) of the second cylindrical portion (65; 65a) is varied such that, to shorten the delay time (t), the diameter (D) of the second cylindrical portion (65; 65a) is increased and, to lengthen the delay time (t), the diameter (D) of the second cylindrical portion (65; 65a) is decreased, to attain equal delay times (t) in fuel injection valves (10; 10a; 60; 60a) with injector housings (11) of different length and with valve needles (40; 40a; 62; 62a) of different length, at least the volume of the control chamber (37) is adapted such that, to shorten the delay time (t), the volume of the control chamber (37) is decreased and, to lengthen the delay time (t), the volume of the control chamber (37) is increased, wherein the diameter (D) of the second cylindrical portion (65; 65a) is varied in diameter steps, and fine adjustment of the delay time (t) is carried out by means of an adaptation of the volume of the control chamber (37) by means of a variation of the length of the second cylindrical portion (65; 65a).
2. Method according to Claim 1,
   characterized
   in that the geometry of the control chamber (37) in the region in which the valve needle (40; 40a; 62; 62a) is guided is in the form of a cylindrical bore (38) with always the same diameter and always the same depth, and in that the volume of the control chamber (37) is adapted by means of a shortening or lengthening of that portion (39; 39a) of the valve needle (40; 40a; 62; 62a) which is guided in the control chamber (37).
3. Method according to Claim 1,
   characterized
   in that, taking into consideration the minimum and maximum possible volume of the control chamber (37) and the available diameter steps of the valve needle (62; 62a), that diameter (D) of the valve needles (62; 62a) is selected which leads to a minimum volume of the control chamber (37).
4. Method according to Claim 3,
   characterized
   in that the ratio of the enlargement of the valve needle stroke ΔH owing to the enlargement of the volume of the control chamber (37) to the shortening of the needle stroke owing to the shortening of the valve needle ΔL is calculated as follows: $$\mathrm{\Delta H}/\mathrm{\Delta L}=\left(\mathrm{E}\left(\mathrm{37}\right)\mathrm{x\; A}\left(\mathrm{37}\right)\right)/(\mathrm{E}\left(\mathrm{65};\mathrm{65}\mathrm{a}\right)\mathrm{x}\left(\mathrm{A}\left(\mathrm{65};\mathrm{65}\mathrm{a}\right)\right),$$

   

   
   where

   E(37) is the modulus of elasticity of the fuel in the region of the control chamber (37),

   A (37) is the cross-sectional area (A) in the region of the control chamber (37),

   E(65; 65a) is the modulus of elasticity of the portion (65; 65a),

   A(65; 65a) is the cross-sectional area (A) in the region of the portion (65; 65a),

   and where
   the ratio ΔH / ΔL lies between 100 and 500.
5. Method according to one of Claims 1, 3 and 4,
   characterized
   in that the second portion (65; 65a) of the valve needle (62; 62a) is connected, on the opposite side from the standardized first portion (63), to a standardized third portion (64).
6. Method according to one of Claims 1, 3, 4 and 5,
   characterized
   in that the connection at least between the second portion (65; 65a) of the valve needle (62; 62a) and the standardized first portion (63) and if appropriate between the second portion (65; 65a) of the valve needle (62; 62a) and the third portion (64) is realized by laser welding.

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