EP0917623A1

EP0917623A1 - Fuel injection valve

Info

Publication number: EP0917623A1
Application number: EP98912280A
Authority: EP
Inventors: Ferdinand Reiter
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1997-06-06
Filing date: 1998-02-20
Publication date: 1999-05-26
Also published as: US6224002B1; JP2000516325A; DE19723953A1; WO1998055763A1

Abstract

The invention relates to a fuel injection valve for fuel injection systems of internal combustion engines, characterised in that the individual component parts are easy and economical to produce. The valve needle (18), which can be moved along the longitudinal valve axis (10), consists essentially of a thin wire (51). Said wire forms the extended downstream continuation of a spiral return spring (20). The valve needle (18) engages in a sealing element (52), said sealing element interacting with a valve seat body (23). Said valve seat body has a fixed valve seat. The valve needle (18) and the sealing element (52) are arranged in relation to the valve seat (23) in such a way that the wire transmits pressure forces onto the sealing element (52) and the valve seat (23) when the valve is in the closed position. The inventive fuel injection valve is particularly suitable for use in fuel injection systems of mixture-compression, spark-ignition internal combustion engines.

Description

Fuel injector

State of the art

The invention relates to a fuel injector according to the preamble of the main claim. From DE-OS 25 08 390 it is already known in a fuel injector to design an axially movable valve needle as a thin, stiff rod or unstiff wire. The rod is integrally connected at its downstream end to a closing head which interacts with a valve seat. At its opposite end, the rod passes through an anchor, being connected to a tension spring upstream of the anchor. The tension spring ensures that when the solenoid coil is not excited, the closing head is pulled up to the valve seat via the rod, so that the valve is in the closed position. If current flows through the solenoid, the armature is attracted and the tension spring is stretched. As a result, the rod moves axially such that the closing head lifts off the valve seat. In order to close the valve again, the tensile forces of the tension spring act when the solenoid coil is not energized.

From DE-OS 34 27 526 and DE-OS 35 35 438 fuel injectors are already known which can be actuated electromagnetically and have a flat armature in their magnetic circuit, DE-OS 34 27 526 also showing a light and elongated valve needle. Advantages of the invention

The fuel injector according to the invention with the characterizing features of the main claim has the

Advantage that it can be manufactured with very simple and inexpensive individual components. The valve needle is advantageously designed as a thin wire which is connected to a sealing element, the sealing element in turn interacting with a valve seat.

It is advantageous that the valve needle and the sealing element are designed in such a way that the wire in the closed position of the valve, that is to say when the sealing element is in contact with the valve seat, transmits compressive forces to the sealing element and the valve seat.

The measures listed in the subclaims allow advantageous developments and improvements of the fuel injector specified in the main claim.

It is particularly advantageous to design the wire serving as a valve needle in one piece as a downstream, elongated continuation of a spiral return spring, by means of the compression spring force of which the sealing element passes over the

Valve needle is brought into the closed position of the valve. In order to increase the bending stiffness of the thin wire, the valve needle is advantageously provided with a support element that is very easy to manufacture. A very high bending stiffness with the smallest possible additional mass is achieved by an L-shaped angle plate, which partially envelops the spring wire lying in the bend of the angle plate. Slipping of the angle plate on the wire is avoided by means of the connecting tabs connecting the two legs of the support element. A non-positive connection is advantageously present between the wire and the sealing element. The wire rounded at its downstream end engages in a recess in the sealing element and thus transmits the compressive forces of the return spring to the sealing element. It is particularly advantageous if the depression is shaped conically, the base of the depression ideally having the same radius as the rounded wire end.

It is also advantageous to design an armature of the electromagnetic circuit as a flat armature, on which the return spring is supported. Due to its low overall height, a flat anchor construction is particularly suitable. The formation of a flat anchor allows the use of a non-magnetic, e.g. austenitic material for a valve seat carrier, which can be deep-drawn much better than a ferritic material, which results in lower production costs.

With the fuel injector according to the invention, it is very easy to represent widely protruding injection points (e.g. already within an intake manifold) (extended tip injector), since the lengths of the deep-drawn valve seat carrier and the spring wire can be varied easily and inexpensively. It is of great advantage that the above-mentioned spray point is achieved with a very small moving mass due to the above-mentioned configuration of the valve needle.

In order to ensure the opening of the injection valve when the solenoid coil is energized, a resilient corrugated washer is arranged between the sealing element and a valve seat body that cooperates with it and has the valve seat, the spring force of which is opposite to the spring force of the return spring works. The sealing element is thus lifted off the valve seat by the corrugated disk. The corrugated disk advantageously has bores, slots or grooves in order to allow the fuel to flow in the direction of the valve seat. In addition, the corrugated washer ensures the radial guidance of the sealing element in the valve seat carrier.

The valve seat body advantageously has a conical opening, into which a perforated spray disk with an at least partially conical configuration can be inserted in a self-centering manner. Complex centering devices for the assembly of the spray orifice plate are therefore not required.

The design of the armature and the valve seat body in a flat design as a flat anchor and flat seat allow relatively large guiding games, which can be produced inexpensively.

This overall constructive design and the associated elimination of welding operations on the sealing element and on the valve seat body permit the use of ceramic for these two components, for example when using aggressive fuels.

drawing

An embodiment of the invention is shown in simplified form in the drawing and explained in more detail in the following description. FIG. 1 shows a fuel injection valve with an inventive one

Valve needle and Figure 2 shows a section along the line II-II in Figure 1.

Description of the embodiment The electromagnetically actuated valve in the form of an injection valve for fuel injection systems of mixture-compressing, spark-ignited internal combustion engines, for example shown in FIG. 1, has a valve that is surrounded by a magnet coil 1 as

Fuel inlet connector serving tubular core 2, which has, for example, a stepped inner and outer diameter over its axial length. A coil body 3 made of plastic takes up a winding of the magnet coil 1 and enables a compact one in connection with the core 2

Structure of the injection valve in the area of the solenoid coil 1.

The core 2, which is formed concentrically with a longitudinal axis 10 of the valve, has in its axially central region a shoulder 11 on its outer contour, on which the core 2 is connected to a metal valve jacket 12, for example by laser welding. The valve jacket 12 is designed so that it extends radially above the magnet coil 1 from the core 2 with an area 13 to surround the magnet coil 1 from the outside when viewed in the downstream direction. The magnet coil 1 is thus embedded between the core 2 and the valve jacket 12. In the downstream direction, the valve jacket 12 is followed by a sleeve-shaped and, for example, stepped valve seat support 16, which is firmly connected to the valve jacket 12. A longitudinal opening 17 runs in the valve seat carrier 16 and is formed concentrically with the longitudinal axis 10 of the valve. While an upper region 17a of the longitudinal opening 17 is designed so far that it can at least partially enclose the valve jacket 12, a lower region 17b of the longitudinal opening 17 is formed with a smaller diameter. A valve needle 18 is arranged mainly in the lower region 17b of the longitudinal opening 17. The injection valve is actuated in a known manner, for example electromagnetically. The electromagnetic circuit with the magnetic coil 1, the core 2, the valve jacket 12 and an armature 21 is used for the axial movement of the valve needle 18 and thus for opening against the spring force of a return spring 20 or closing the injection valve. The armature 21 is designed in the form of a flat armature , connected to the upstream end of the valve needle 18 and aligned with the core 2. In the downstream end of the valve seat carrier 16 facing away from the core 2, a cylindrical valve seat body 23, which has a fixed valve seat, is mounted in the longitudinal opening 17.

The as an inlet connector for fuel and stop for the

The armature 21 serving core 2 has a smaller outer diameter starting from the shoulder 11 in the downstream direction than upstream of the shoulder 11, as a result of which the injection valve also has a comparatively small outer diameter in the area of the magnet coil 1. The core 2 represents either a turned part or a deep-drawn ferritic tube. A lower stop surface 25 facing the armature 21 is, for example, hard chrome-plated or chemically nickel-plated. The valve jacket 12, which resembles a guide pot, is present, for example, as a deep-drawn, ferromagnetic component. In its area 13, which is designed radially above the magnetic coil 1, the valve jacket 12 has a cutout 26 through which contact pins 27 extending from the magnetic coil 1 are passed. On its outer contour, the valve jacket 12 has, for example, specially designed sections below the region 13, namely an upper section 12a which has circumferential grooves 28 to ensure a positive fit with a plastic extrusion 30, and a lower section 12b which deepens is designed to be able to receive the valve seat carrier 16 with a precise fit. A lower pole face 31 of the valve jacket 12, like the stop face 25, is hard chrome-plated or chemically nickel-plated, the two faces 25 and 31 lying in one plane, for example.

The coil former 3 ensures good heat dissipation and a low risk of damage to the winding of the magnetic coil 1. In the direction of the armature 21, two ring lugs 33 extend out of the coil former 3, so that three

Annular chambers 34 are formed between the two annular lugs 33 themselves and between the inner annular lug 33 and the core 2 and the outer annular lug 33 and the valve jacket 12. In the inner and the outer annular chamber 34, a sealing ring 35 is inserted, which e.g. is designed as an O-ring. This measure ensures that the magnet coil 1 is dry. The axial fixation of the sealing rings 35 takes place in that a holding ring 36, which has a T-shaped cross section, is arranged between the magnetic coil 1 and the armature 21, an axially extending arm engaging in the central annular chamber 34 between the two annular lugs 33. The radially extending arms of the retaining ring 36 press against the sealing rings 35.

The anchor 21, designed as a flat anchor, is in the form of a thin, circular disk which is punched out, for example, from a larger sheet. A central through opening 38 serves the fuel throughflow, which flows from the core 2 in the direction of the valve seat, and the passage of a spring wire 51 of the valve needle 18. Outside the central through opening 38, further holes 39 are provided in a circle in the armature 21, with which a reduction of so-called Splash losses due to the otherwise excessive flow resistance in the anchor area. On the upstream side of the armature 21 the passage opening 38 has an embossed shoulder 40 on which the return spring 20 is supported. Like the stop surface 25 and the pole surface 31, the upstream end face of the armature 21 opposite these surfaces is surface-coated, for example hard chrome-plated or chemically nickel-plated, in order to guarantee adequate wear protection. The valve seat support 16 is made with its inner longitudinal opening 17 such that the upper region 17a takes over the radial guidance of the armature 21.

An adjusting sleeve 43 inserted into a flow bore 42 of the core 2 concentric to the longitudinal axis 10 of the valve serves to adjust the spring preload of the return spring 20 resting on the adjusting sleeve 43, which is supported with its opposite side on the shoulder 40 of the armature 21.

Arranged downstream of the armature 21 in the longitudinal opening 17 of the valve seat carrier 16 is a plate spring 45, which holds the armature 21 in its initial position in the de-energized state and has a spring force effect against the return spring 20. The plate spring 45, for example manufactured by stamping and bending, is equipped with an outer ring 47 and an inner ring 48, each of which has an annular shape. Both rings 47 and 48 are connected to each other by several spokes arranged through 360 °. When the solenoid 1 is energized, the plate spring 45 supports the tightening movement of the armature 21 against the spring force of the return spring 20. In addition, the plate spring 45 prevents the armature 21 from wobbling. In addition to guiding the armature 21, the valve seat support 16 with the upper region 17a ensures the radial Guiding the plate spring 45. While the slightly curved outer ring 47 is supported on the lower end face of the armature 21 outside the holes 39, the Inner ring 48 of the plate spring 45 on a shoulder 49 of the valve seat carrier 16 which extends radially between the regions 17a and 17b. For example, the inner bending radius between the shoulder 49 and the lower area 17b facing the valve longitudinal axis 10 is suitable as the contact area.

The wire 51 serving as valve needle 18, in particular spring wire, provides the e.g. is a one-piece continuation of the return spring 20, which extends helically up to the shoulder 40 of the armature 21 and from there extends axially elongated in the downstream direction. At its downstream end, the valve needle 18 is rounded, for example, to fit into a middle, e.g. engage conical recess 50 of a sealing element 52. The valve needle 18 transmits the spring force (compressive force) of the return spring 20 to the sealing element 52. The disk-shaped sealing element 52 interacts with the valve seat body 23 and forms a seat valve.

As kink protection for the very thin spring wire 51, the valve needle 18 has an additional angled, in

Cross section of L-shaped support element 53. The support element 53 is a sheet metal which is bent in a simple manner and which surrounds the spring wire 51 at approximately a right angle over most of the axial extension of the valve needle 18. As illustrated in FIG. 2 as a section along the line II-II in FIG. 1, stabilization of the spring wire 51 is achieved, for example, by connecting tabs 54 being clamped in the kink of the support element 53 and connecting the two legs of the support element 53. On the other hand, the spring wire 51 of the valve needle 18 can also be firmly connected to the support element 53 by welding, soldering or gluing. In a simple manner, a high bending stiffness of the valve needle 18 is achieved with a support element 53. The disk-shaped sealing element 52 has on its lower end face 56, which faces the valve seat body 23, an outer, completely circumferential recess 57, in which an annular, resilient corrugated disk 58 is arranged. The lower end face 56 of the sealing element 52 made, for example, of a stainless steel or ceramic, which serves as a sealing side interacting with the valve seat body 23, is very precisely machined, for example lapped, except in the region of the recess 57. The radial guidance of the sealing element 52 during its axial movement along the longitudinal valve axis 10 takes place through the corrugated disk 58 in the region 17b of the valve seat support 16.

In addition to guiding the sealing element 52, the corrugated disk 58 primarily has the task of lifting the sealing element 52 off the valve seat body 23 when the magnet coil 1 is excited. When the magnet coil 1 is not energized and the valve is closed, there is a frictional connection between the spring wire 51 and the sealing element 52 and the sealing element 52 and valve seat body 23 due to the pressure force effect of the return spring 20, since the spring force is transmitted to the sealing element 52 via the valve needle 18. If the solenoid coil 1 is now energized, the armature 21 is attracted against the spring force of the return spring 20, the valve needle 18 being forced to move axially. This movement of the valve needle 18 would result in the spring wire 51 lifting off the sealing element 52 and the sealing element 52 itself remaining on the valve seat body 23. Due to the spring washer 58 having a spring force against the spring force of the return spring 20, the sealing element 52 follows the movement of the valve needle 18, and that

Valve opens when armature 21 is attracted. Corrugated washer 58 can advantageously absorb and store axial forces very well. In the corrugated disk 58 there are, for example, a plurality of openings in the form of bores, slots or Grooves are provided through which the fuel can flow to the valve seat body 23.

The sealing element 52 and the valve seat body 23 are, for example, made of the same material, e.g. made of stainless steel or ceramic. At its lower end 59, the valve seat support 16 has a bulge 60 with a larger inner diameter than in the region 17b, into which the valve seat body 23 is inserted with exact dimensions. In this case, the valve seat body 23 can still rest against an inclined surface 62 of the bulge 60 which serves as a stop. On the upper end face of the valve seat body 23 facing the sealing element 52, small depressions are made in such a way that at least two raised areas are formed, on the one hand an outer support area 65 and on the other hand an inner sealing area 66. The two areas 65 and 66 represent e.g. concentric rings, with the outer support region 65 serving as a support for the corrugated washer 58 and the inner sealing region 66 interacting directly as a sealing surface with the lower end face 56 of the sealing element 52. The sealing area 66 is precisely finished in accordance with the requirements for the tightness of the valve, e.g. lapped. Starting from a central cylindrical opening 68 on the upper end face, the valve seat body 23 closes in a downstream direction

Opening area 69 widening in the direction of a truncated cone. The flat anchor and the flat seat construction allow relatively large guiding games that can be produced inexpensively.

On its lower end facing away from the sealing element 52, the valve seat body 29 is provided with a spray-perforated disk 75, for example in the form of a pot. The spray hole disk 75 nestles above all against the wall of the conical opening area 69, while it has a circumferential flat holding edge 76 radially outside the opening region 69. In the area of the holding edge 76, a sealing ring 77 is arranged, for example, between the valve seat body 23, the bulge 60 of the valve seat support 16 and the spray hole disk 75 for sealing the seat area. Immediately downstream of the opening 68, at least one, for example four, spray openings 78 formed by eroding or stamping are provided in a largely flat bottom region of the spray perforated disk 75 near the valve longitudinal axis 10. The largely conical design within the opening area 69 is very advantageous for self-centering of the spray perforated disk 75. The cone angle of the spray hole disk 75 is approximately 2 ° smaller than the cone angle of the opening region 69 of the valve seat body 23. The spray hole disk 75 is fastened, for example, by a support disk 79 arranged downstream, which is designed in a circular shape and the holding edge 76 of the spray hole disk 75 between itself and the valve seat body 23 is jammed. By flanging the end 59 of the bulge 60 below the support disk 79, a simple and secure fixation of the spray perforated disk 75 or the support disk 79 is ensured. On the other hand, it is also conceivable to connect the spray hole disk 75, which is in the form of a pot, to the valve seat body 23 concentrically and firmly, for example by means of a circumferential, dense weld seam, for example formed by a laser.

The, for example, deep-drawn valve seat support 16 consists of a non-magnetic austenitic material. in the

Area 17a, the valve seat support 16 in the recessed section 12b is tightly and firmly connected to the valve jacket 12, for example by a weld seam formed by a laser. The insertion depth of the valve seat body 23 determines the presetting of the stroke of the valve needle 18. Die precise stroke adjustment is carried out by plastic deformation of the radially extending shoulder 49 of the valve seat carrier 16 in the axial direction. The one end position of the valve needle 18 when the magnet coil 1 is not energized is determined by the contact of the sealing element 52 on the valve seat body 23, while the other end position of the valve needle 18 when the magnet coil 1 is energized results from the contact of the armature 21 on the stop surface 25 of the core 2.

Upstream of the coil area, the injection valve is enclosed with plastic encapsulation 30, which encases the core 2 over a larger area and extends in the axial direction up to section 12a of the valve jacket 12, the valve jacket 12 being partially covered axially and in the circumferential direction. To this

Plastic encapsulation 30 includes, for example, an injection-molded electrical connector plug 82, in which the two contact pins 27 which start from the magnet coil 1 and serve to excite the magnet coil 1 end.

At the inlet end of the injection valve, a fuel filter 83 projects into the flow bore 42 of the core 2. The fuel entering the fuel injection valve flows through the fuel filter 42 in a known manner and exits the fuel filter 42 in the radial direction. The fuel filter 42 ensures that those particles carried in the fuel are filtered out, which, because of their size or chemical composition, could cause blockages or damage in the injection valve.

Claims

claims

1. Fuel injection valve for fuel injection systems of internal combustion engines, with a valve longitudinal axis, with a valve needle movable along the valve longitudinal axis, which has a thin wire, and an axially movable sealing element, which cooperates with a valve seat, the valve being in the closed position when the sealing element on the valve seat abuts, characterized in that the valve needle (18) and the sealing element (52) are designed such that the wire (51) in the closed position of the valve transfers compressive forces to the sealing element (52) and the valve seat (23).

2. Fuel injector according to claim 1, characterized in that the valve needle (18) forming wire as a spring wire (51) is integrally formed with a return spring (20), by the spring force of the sealing element

(52) is held in a position against the valve seat (23).

3. Fuel injection valve according to claim 2, characterized in that the valve needle (18) is a support element

(53) to increase the bending stiffness of the wire (51).

4. Fuel injection valve according to claim 3, characterized in that the support element (53) is an L-shaped sheet metal part which has two legs which in its Kink the wire (51) with the help of at least one connecting strap (54).

5. Fuel injection valve according to one of claims 2 to 4, characterized in that there is a non-positive connection between the wire (51) and the sealing element (52).

6. A fuel injector according to claim 5, characterized in that the wire (51) is rounded at its downstream end and engages with this end in a recess (50) of the sealing element (52).

7. Fuel injection valve according to claim 6, characterized in that the recess (50) in the sealing element (52) is conical.

8. Fuel injection valve according to claim 2, characterized in that the return spring (20) abuts a shoulder (40) of an armature (21) which is designed as a flat armature.

9. Fuel injection valve according to one of the preceding claims, characterized in that the sealing element (52) is disc-shaped.

10. Fuel injection valve according to claim 9, characterized in that between the sealing element (52) and a cooperating with it, the valve seat having valve seat body (23), a resilient corrugated washer (58) is arranged which for lifting the sealing element (52) from the valve seat ( 23) exerts a force on the sealing element (52) from the closed position.

11. Fuel injection valve according to claim 10, characterized in that the sealing element (52) and / or the valve seat body (23) can be produced from ceramic.

12. The fuel injector according to claim 10, characterized in that the valve seat body (23) has a conical opening (69) into which an orifice plate (75) with at least partially conical design can be used self-centering.

13. Fuel injection valve according to claim 12, characterized in that the spray orifice plate (75) can be fastened by clamping on the valve seat body (23).