EP1112446B1 - Fuel injection valve - Google Patents

Description

State of the art

The invention is based on a fuel injector according to the genus of the main claim.

DE 38 08 635 A1 is already an electromagnetic one actuatable fuel injector known in which a trained on an axially movable valve needle Valve closing section with a fixed valve seat for opening and closing of the valve interacts. The Valve closing section is in the downstream direction Tapered while the valve seat runs frustoconical. This valve closing section forms the downstream end of the valve needle, which in a Cone tip runs out. Upstream of the The valve closing section or the valve seat is the Valve needle with several spiral fuel channels provided by which the fuel to be sprayed swirled to the valve seat to atomize the To improve fuel and the To control fuel flow rate.

In addition to the tapered, pointed downstream end of the Valve needle is, for example, from US Pat. No. 5,350,119 Fuel injector with an axially movable Valve needle known to have a rounded Has valve closing portion which is the downstream end the valve needle forms.

Furthermore, DE 30 46 889 C2 discloses a Fuel injector with a flat armature and one attached fastening part to provide. This movable valve member acts with a housing-fixed Valve seat together. The closure part has a convex molded valve closing section by a Flat bevels running perpendicular to the longitudinal axis of the valve is completed. Downstream of the valve seat is a Collection space provided, the volume of which should be as small as possible should and through the valve seat body, the flat lower Limitation of the valve closing section and the opposite flat upper boundary surface of a Swirl body arranged downstream of the valve seat body is limited. There are several swirl channels in the swirl body introduced that begin on the side of the swirl body and in a central swirl chamber open.

From JP 10047210 A is already a Fuel injection valve for fuel injection systems from Internal combustion engines known to be an excitable Actuator and one axially along one Valve longitudinal axis movable valve needle, which on its has a valve closing section downstream end, the one for opening and closing the valve with a fixed Valve seat cooperates. The valve seat is included formed on a flat valve seat element. Upstream of the valve seat, the valve has one Swirl body, on the one hand as a guide for the valve needle serves and on the other hand the fuel to be sprayed Twist impresses. Downstream of the valve seat is at downstream end of the valve closing section a Flattening perpendicular to the longitudinal axis of the valve intended. One closes to the valve seat Exit opening, which has a diameter D, the is significantly larger than the diameter of the Flattened valve needle.

Advantages of the invention

The fuel injector according to the invention with the characteristic features of the main claim has the Advantage that compared to known valves with a Swirl generation in the fuel upstream of the valve seat improved fuel processing is achieved. In particular concerns the improvement of Preparation quality the so-called pre-jet. This Vorstrahl is formed by fuel that is at closed valve in an inner swirl chamber of the swirl-generating agent has collected in front of the valve seat. This fuel largely flows when the valve is opened axial and not twisted to a downstream of the Valve seat arranged outlet opening. With the Measures according to the invention is effectively a better one Preparation of the fuel in the pre-jet enables. The fact is exploited that the pre-beam starting flow and the formation of a Wall film in the outlet opening very strongly through the Design of the valve needle tip that defines the flow area the swirl flow, can be influenced. On the droplet size can be reduced are sprayed, which means a finer fuel spray becomes. Due to the energy loss of the fuel at the Flattening the valve needle becomes the more harmful The beam length is reduced. Across the street tapered or rounded valve needle ends are created in advantageously a shortened beam with less Penetration.

In addition, an increase in the homogeneity of the the following swirling main jet is pointed reach tapered or rounded valve needle ends.

By the measures listed in the subclaims advantageous further developments and improvements of the Main claim specified fuel injector possible.

It when the diameter d is the most advantageous downstream end of the valve needle Flattening with a known size of the outlet opening with the Diameter D is selected so that the ratio d / D is approx. Is 1.5.

Advantageously, the swirl-generating means are as disc-shaped swirl element that is very simple structured and therefore easy to form. in the Compared to swirl bodies that have grooves on one end face or have similar swirl-generating depressions an inner one in the swirl element with the simplest of means Opening area can be created that extends across the entire extends axial thickness of the swirl element and from one outer peripheral edge area is surrounded.

Just like the swirl element and the valve seat element the guide element is also easy to manufacture. Especially the guide element advantageously serves with a inner guide opening of the leadership of the projecting Valve needle. By training the guide element on outer circumference with alternating tooth-like protruding Areas and intermediate recesses is open created a simple way to get an optimal one Inflow into the swirl channels of the one below guarantee parallel elements.

drawing

Embodiments of the invention are in the drawing shown in simplified form and in the following Description explained in more detail. 1 shows a first Embodiment of a fuel injector, figure 2 shows a second example of a fuel injector, only the downstream valve end is shown, Figure 3 a first leadership and seating area as an enlarged Detail from Figure 2, Figure 4 a second guide and Seating area, Figure 5 shows a third leadership and Seating area, Figure 6 a Swirl element and Figure 7 is a guide element which in Fuel injection valves according to Figures 1 to 5 can be used are.

Description of the embodiments

That in Figure 1, for example, as a Embodiment shown electromagnetically actuatable valve in the form of an injection valve for Fuel injection systems from spark-ignited Internal combustion engines have one of a magnetic coil 1 at least partially surrounded, as the inner pole of one Serving magnetic circuit, tubular, largely hollow cylindrical core 2. The fuel injector is particularly suitable as a high pressure injection valve for direct injection of fuel into a combustion chamber Internal combustion engine. For example, a tiered one Plastic bobbin 3 takes a winding of Magnetic coil 1 and allows in connection with the core 2 and an annular, non-magnetic, from the Magnetic coil 1 partially surrounded intermediate part 4 with a L-shaped cross section a particularly compact and short Structure of the injection valve in the area of the solenoid coil 1.

There is a continuous longitudinal opening 7 in the core 2 provided, which extends along a valve longitudinal axis 8 extends. The core 2 of the magnetic circuit also serves as Fuel inlet port, the longitudinal opening 7 a Represents fuel supply channel. With the core 2 above the Solenoid 1 is firmly connected to an outer metal (e.g. ferritic) housing part 14, which as the outer pole or outer guide element closes the magnetic circuit and the Solenoid 1 completely at least in the circumferential direction surrounds. In the longitudinal opening 7 of the core 2 is on the inlet side a fuel filter 15 is provided for the Filtering out such fuel components ensures that due to their size in the injector clogging or Could cause damage. The fuel filter 15 is z. B. fixed by pressing in the core 2.

The core 2 forms with the housing part 14 that on the inlet side End of the fuel injector, with the upper Housing part 14, for example in the axial direction seen just downstream via the magnetic coil 1 extends beyond. The upper housing part 14 closes tight and tight to a lower tubular housing part 18, the Z. B. consists of an axially movable valve part an armature 19 and a rod-shaped valve needle 20 or encloses an elongated valve seat support 21 or receives. The two housing parts 14 and 18 are, for. B. with a circumferential weld seam firmly connected.

In the exemplary embodiment shown in FIG. 1, these are lower housing part 18 and the largely tubular Valve seat carrier 21 firmly screwed together connected; Welding, soldering or flanging also do the job possible joining processes. The seal between the Housing part 18 and the valve seat support 21 takes place, for. B. by means of a sealing ring 22. The valve seat support 21 has an inner one over its entire axial extent Through opening 24 which is concentric with the Valve longitudinal axis 8 runs.

With its lower end 25, which also the downstream completion of the whole Fuel injector, surrounds the Valve seat carrier 21 in the through opening 24 fitted disc-shaped valve seat element 26 with a narrowing frustoconically downstream Valve seat surface 27. In the through opening 24 is the z. B. rod-shaped, a largely circular Cross-section valve needle 20 arranged, the a valve closing section 28 at its downstream end having. This, for example, spherical or partial spherical or rounded or tapered tapered valve closing section 28 acts in a known manner Way with that provided in the valve seat member 26 Valve seat surface 27 together. The valve closing section 28 when the downstream end of valve needle 20 ends downstream with a flattening 29 according to the invention, the is flat and perpendicular to the valve longitudinal axis 8 runs. The flattening 29 is e.g. around a flat sanding. Downstream of the Valve seat surface 27 is at least in valve seat element 26 an outlet opening 32 is introduced for the fuel.

The injection valve is actuated in a known manner Way electromagnetic. A piezo actuator or a magnetostrictive actuator as excitable actuators are also conceivable. An operation is also over a controlled pressure-loaded piston is conceivable. For axial Movement of the valve needle 20 and thus against opening the spring force of one in the longitudinal opening 7 of the core 2 arranged return spring 33 or closing the Injector serves the electromagnetic circuit with the Solenoid 1, the core 2, the housing parts 14 and 18 and the anchor 19. The anchor 19 is with the Valve closing section 28 facing away from the end of the valve needle 20 z. B. connected by a weld and on the core 2nd aligned. To guide the valve needle 20 during their Axial movement with the armature 19 along the longitudinal axis of the valve 8 serves on the one hand in the valve seat support 21 on the armature 19 facing end provided guide opening 34 and on the other hand, an upstream of the valve seat member 26 arranged disc-shaped guide element 35 with a dimensionally accurate guide opening 55. The anchor 19 is during its axial movement surrounded by the intermediate part 4.

Between the guide element 35 and the valve seat element 26 is another disc-shaped element, namely a Swirl element 47 arranged so that all three elements 35, 47 and 26 lie directly on top of each other and in Find valve seat bracket 21. The three disc-shaped elements 35, 47 and 26 are for example firmly bonded together.

A inserted in the longitudinal opening 7 of the core 2, Pressed or screwed adjusting sleeve 38 is used Setting the spring preload using a centering piece 39 with its upstream side on the adjusting sleeve 38 adjacent return spring 33, which with their opposite side is supported on the anchor 19. At anchor 19 are one or more bore-like flow channels 40 provided through which the fuel from the longitudinal opening 7th in the core 2 from downstream of the flow channels 40 trained connecting channels 41 near the guide opening 34 in the valve seat support 21 into the through opening 24 can reach.

The stroke of the valve needle 20 is determined by the installation position of the Valve seat element 26 predetermined. A final position of the Valve needle 20 is through when magnet coil 1 is not energized the installation of the valve closing section 28 on the Valve seat surface 27 of the valve seat element 26 fixed, while the other end position of the valve needle 20 at excited solenoid 1 by the system of the armature 19 on the downstream end of the core 2 results. The Surfaces of the components in the latter stop area are chrome-plated, for example.

The electrical contacting of the magnetic coil 1 and thus their excitation takes place via contact elements 43, which are still outside of the bobbin 3 with a Plastic extrusion 44 are provided. The Plastic encapsulation 44 can also be used for other Components (e.g. housing parts 14 and 18) of the Extend fuel injector. From the Plastic extrusion 44 runs an electrical Connection cable 45, via which the energization of the magnetic coil 1 he follows. The plastic extrusion 44 protrudes through the in Upper housing part 14 interrupted in this area.

Figure 2 shows a second embodiment of a Fuel injector, with only the downstream Valve end is shown. In contrast to that in Figure 1 illustrated example are in the valve seat support 21 in Area of the guide opening 34 several axially parallel extending connecting channels 41 are provided. To be safe To allow flow into the valve seat support 21 is the passage opening 24 with a larger diameter trained, while the valve seat support 21 thin-walled is executed.

In Figure 3, the leadership and seating area is a cutout shown in Figure 2 again in a changed scale to this valve area with the designed according to the invention Clarify valve needle end better. The one in spray-side end 25 of the valve seat carrier 21 in its Through opening 24 provided guide and seating area is in the embodiment shown in Figure 3 through three axially successive, disc-shaped, functionally separate elements formed that are fixed to each other are connected. Follow in the downstream direction successively the guide element 35, the very flat Swirl element 47 and valve seat element 26.

The valve seat element 26 partially has one Outside diameter on that it taut with little play in a lower portion 49 of the through opening 24 of the Valve seat support 21 downstream one in the Through opening 24 provided stage 51 can be fitted can. The guide element 35 and the swirl element 47 have, for example, a slightly smaller one Outside diameter as the valve seat member 26.

The guide element 35 has a dimensionally accurate inner Guide opening 55 through which the valve needle 20th moved through during their axial movement. From the outside The guide element 35 has a circumference over the circumference distributes several recesses 56, one of which Fuel flow on the outer periphery of the guide member 35 along into the swirl element 47 and further in the direction to the valve seat surface 27 is guaranteed. Based on the figures 7 and 8 each is an embodiment of the swirl element 47 or the guide element 35 described in more detail.

The three elements 35, 47 and 26 lie directly with theirs respective end faces to each other and already exist their assembly in the valve seat bracket 21 firmly together connected before. The solid connection of the individual disc-shaped elements 35, 47 and 26 takes place cohesively on the outer circumference of the elements 35, 47, 26, welding or bonding are preferred joining methods. In the example shown in FIG. 3 there are welding spots or short weld seams 60 in the peripheral areas provided in which the guide member 35 none Has recesses 56. After connecting the three Elements 35, 47, 26 are the Guide opening 55, the valve seat surface 27 and the upper End face 59 of the guide element 35 ground. Consequently these three areas have a very small area Concentricity deviation from each other.

The entire multi-disc valve body is, for example inserted into the through opening 24 until the upper end face 59 of the guide element 35 on the step 51 is applied. The valve body is attached e.g. by means of a weld seam 61 achieved by means of a laser lower end of the valve between valve seat element 26 and valve seat bracket 21.

According to the downstream end of the Valve closing section 28 and thus the entire Valve needle 20 with the perpendicular to the valve longitudinal axis 8 provided flattening 29. The one on the valve pin 20 provided flat 29 has a diameter d, which is larger than the diameter D which is downstream subsequent outlet opening 32, so that d> D applies. It when the diameter d is particularly advantageous known size of the outlet opening 32 is selected that the ratio d / D is about 1.5. At a Swirl generation upstream of the valve seat surface 27 result each time the valve is opened by lifting the Valve closing section 28 from valve seat surface 27 subsequently two successive jet types. When opening the valve, a so-called first occurs Pre-jet into the outlet opening 32. This pre-beam is formed by fuel, which is when closed Valve in an inner swirl chamber 92 of swirl element 47 collected in front of the valve seat. This fuel flows when opening the valve largely axially and not twisted to the outlet opening 32. Only immediately then the main beam follows that is formed by fuel that swirl element 47 flowed through directly beforehand and the corresponding is twisted.

The flattening 29 on the valve needle 20 now causes in advantageously an improved preparation of the Vorstrahles because the flattening 29 is a vortexing of the Allows fuel. In this way, the Droplet size can be reduced, creating a finer Fuel spray is sprayed. In addition, one can Increasing the homogeneity of the main beam compared to pointed reach tapered or rounded valve needle ends. It should be explicitly stated that for the Invention the type of training upstream of the Valve seat 27 arranged swirl elements 47 none Influence. Instead of the disk-shaped shown Swirl elements 47 can also have swirl-generating means in completely arbitrary design (e.g. cylindrical Swirl body, swirl grooves on the valve needle) become.

In the further exemplary embodiments of the following Figures are the opposite of that in Figures 2 and 3 illustrated embodiment constant or equivalent parts by the same reference numerals characterized. The main differences are in the Formation of the outlet opening 32 in the valve seat element 26 and the attachment of the valve seat member 26 on Valve seat support 21 before, but not in the formation of the valve needle end according to the invention.

In the example shown in FIG. 4, this has Valve seat element 26 has a circumferential flange 64, which engages downstream end of the valve seat support 21. The top 65 of the circumferential flange 64 is in one Clamping with the guide opening 55 and Valve seat surface 27 ground. The insertion of the three-disc valve body takes place until the Top 65 of the flange 64 at the end 25 of the Valve seat carrier 21. In this investment area both Components 21 and 26 welded together. The Exit opening 32 is e.g. inclined towards Valve longitudinal axis 8 introduced, wherein it downstream in a convexly curved spray region 66 ends.

The example shown in FIG. 5 essentially corresponds the example shown in Figure 4, the essential Difference is that now an additional fourth disc-shaped spray element 67 in the form of a Spray plate is provided, which is the outlet opening 32 has. In comparison to FIG. 4, that is Valve seat element 26 downstream of valve seat surface 27 divided again. The spray 67 and that Valve seat element 26 are e.g. via a means Laser welding achieved weld seam 68 firmly with one another connected, the weld being in a ring circumferential recess 69 is made. Next to the Laser welding is also bonding or resistance welding et al suitable joining methods for this connection. in the Area of the top 65 'of the spray 67 and End 25 of the valve seat support 21, both components are fixed connected to each other (weld 61).

The valve seat element 26 has wear protection reasons has a high carbon content and is highly rewarded. from that the weldability is less good. The Spraying element 67, on the other hand, is made of a weldable one Material made. The weld 68 must also only be slightly resilient. The outlet opening 32 can inexpensive late in the manufacturing process e.g. by drilling be introduced. At the entrance to the exit opening 32 there is a sharp hole edge due to the turbulence in the flow are generated, from which an atomization in particularly fine droplets result.

In Figure 6 is between the guide member 35 and Valve seat element 26 embedded swirl element 47 as Individual component shown in a plan view. The Swirl element 47 can be inexpensively, for example, by means of Stamping, wire EDM, laser cutting, etching or others known methods from a sheet or by galvanic Deposition. In the swirl element 47 an inner opening area 90 is formed, which over the entire axial thickness of the swirl element 47 extends. The Opening area 90 is surrounded by an inner swirl chamber 92, through which the valve closing section 28 of the valve needle extends 20 extends through, and from a variety of in the Swirl chamber 92 opening swirl channels 93 are formed. The Swirl channels 93 open tangentially into swirl chamber 92 and stand with their ends 95 facing away from the swirl chamber 92 not with the outer circumference of the swirl element 47 in Connection. Rather, there remains between the as Inlet pockets formed ends 95 of the swirl channels 93 and the outer circumference of the swirl element 47 a circumferential Border area 96.

When the valve needle 20 is installed, the swirl chamber 92 becomes inside of the valve needle 20 (valve closing section 28) and outwards through the wall of the opening area 90 of the Swirl elements 47 limited. Through the tangential junction the swirl channels 93 in the swirl chamber 92 get the Fuel imprinted an angular momentum, which in the further Flow is maintained up to the outlet opening 32. The centrifugal force makes the fuel hollow-conical hosed. The ends 95 of the swirl channels 93 serve as Collection bags, which are a reservoir for large areas form low-turbulence inflow of fuel. After Flow deflection occurs slowly and the fuel low turbulence into the tangential swirl channels 93 a, whereby a largely trouble-free swirl can be generated is.

Figure 7 is an embodiment of a Guide element 35 removable. About its outer circumference the guide element 35 has alternating recesses 56 and tooth-like protruding areas 98. The tooth-shaped Areas 98 can be rounded. The Manufacturing of the guide element 35 takes place e.g. by Punching. In the example according to FIG. 7, the Recess base 99 inclined so that the Recess base 99 advantageously perpendicular to the Axes of the swirl channels 93 of the underlying one Swirl elements 47 run.

Claims (10)

1. Fuel injection valve for fuel injection systems of internal combustion engines, in particular for the direct injection of fuel into a combustion chamber of an internal combustion engine, having an excitable actuating element (1, 2, 19), having a valve needle (20) which can move axially along a valve longitudinal axis (8) and which has, at its downstream end, a valve-closing section (28) which, for the purpose of opening and closing the valve, interacts with a fixed valve seat (27), the valve seat (27) being formed on a valve seat element (26), and, downstream of the valve seat (27) at the downstream end of the valve-closing section (28), a flattened portion (29) running perpendicularly with respect to the valve longitudinal axis (8) being provided, having swirl-generating means (47, 93) arranged upstream of the valve seat (27), and having an outlet opening (32) adjoining downstream of the valve seat (27), characterized in that the flattened portion (29) has a diameter d which is larger than the diameter D of the outlet opening (32) adjoining downstream.
2. Fuel injection valve according to Claim 1, characterized in that the diameter d of the flattened portion (29) and the diameter D of the outlet opening (32) are selected in such a manner that the ratio d/D is approximately 1.5.
3. Fuel injection valve according to Claim 1, characterized in that the valve-closing section (28) is at least partially bulbous or spherical or rounded and the flattened portion (29) adjoins this convex region.
4. Fuel injection valve according to Claim 1, characterized in that the valve-closing section (28) is designed such that it at least partially tapers in the shape of a truncated cone in the downstream direction and the flattened portion (29) adjoins this conical region.
5. Fuel injection valve according to one of the preceding claims, characterized in that the swirl-generating means are designed in the form of a disc-shaped swirl element (47) directly upstream of the valve seat (27).
6. Fuel injection valve according to Claim 1, characterized in that the outlet opening (32) is formed in the valve seat element (26).
7. Fuel injection valve according to Claim 1, characterized in that an injection element (67) which is connected fixedly to the valve seat element (26) and which has the outlet opening (32) is arranged downstream of the said valve seat element (26).
8. Fuel injection valve according to Claim 5, characterized in that the swirl element (47) has an inner opening region (90) having a plurality of swirl channels (93) which extend completely over the entire axial thickness of the swirl element (47), the swirl channels (93) not being connected to the outer circumference of the swirl element (47) because of a peripheral edge region (96).
9. Fuel injection valve according to Claim 8, characterized in that the inner opening region (90) is formed by an inner swirl chamber (92) and by a multiplicity of swirl channels (93) opening into the swirl chamber (92).
10. Fuel injection valve according to Claim 9, characterized in that the swirl channels (93) have ends (95) which lie remote from the swirl chamber (92) and have, as entry pockets, a larger cross section than the rest of the swirl channels (93).

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