EP0683862A1

EP0683862A1 - Electromagnetic valve

Info

Publication number: EP0683862A1
Application number: EP95900661A
Authority: EP
Inventors: Ferdinand Reiter; Martin Maier; Jörg HEYSE; Norbert Keim
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1993-12-09
Filing date: 1994-11-24
Publication date: 1995-11-29
Anticipated expiration: 2014-11-24
Also published as: EP0683862B1; WO1995016126A1; JP2005337266A; JP3742651B2; CN1116871A; RU2131549C1; JPH08506877A; CN1049951C; CZ197795A3; CZ285156B6; ES2118531T3; BR9406079A; US5732888A; JP3864175B2

Abstract

In already known fuel injection valves, wearing parts such as the armature and the core are provided with wear-resistant layers made for example of chromium, molybdenum or nickel. If the parts of the injection valve are galvanically coated, a desired wedge-shaped distribution of the layer thicknesses is achieved that creates only a small bearing area but which is physically predetermined and practically impossible to influence. The new valve has at lest one part, for example the armature (27) that has a wedge-shaped surface before the wear-resistant layer is applied. The wedge-shaped surface may be produced in a variable manner depending on the desired optimum magnetic and hydraulic properties. The ring-shaped bearing section (68) formed by the wedge has a defined bearing surface or contact width (a) that remains constant during the whole service life of the part, as wearing of the bearing surface in continuous duty does not cause the contact width to increase. This valve is particularly suitable for use in fuel injection systems of mixture-compressing, spark-ignited internal combustion engines.

Description

Electromagnetically actuated valve

State of the art

The invention is based on an electromagnetically actuated valve according to the preamble of the main claim. Various electromagnetically actuated valves, in particular fuel injection valves, are already known, in which components subject to wear are provided with wear-resistant layers.

It is already known from DE-OS 29 42 928 to apply wear-resistant diamagnetic material layers to parts subject to wear, such as anchors and nozzle bodies. These applied layers serve to limit the stroke of the valve needle, thereby minimizing the effects of the residual magnetism on the moving parts of the fuel injector.

From DE-OS 32 30 844 it is also known to provide the armature and stop surface of a fuel injector with wear-resistant surfaces. These surfaces can, for example, be nickel-plated, that is to say provided with an additional layer, or nitrided, that is to say hardened by the incorporation of nitrogen. In addition, it is already known from DE-OS 37 16 072 to use hard molybdenum layers for parts of an injection valve which are particularly stressed by wear and corrosion and which are thin and can be subsequently machined with diamonds.

DE-OS 38 10 826 describes a fuel injection valve in which at least one stop surface is designed in the shape of a spherical cap in order to achieve an extremely precise air gap, a round-body insert made of non-magnetic, high-strength material being formed in the center of the stop surface.

A fuel injection valve is also known from EP-OS 0 536 773, in which a hard metal layer is applied to the armature on its cylindrical peripheral surface and annular stop surface by electroplating. This layer of chrome or nickel has a thickness of 15 to 25 μm, for example. As a result of the galvanic coating, a slightly wedge-shaped layer thickness distribution occurs, with a minimally thicker layer being achieved on the outer edges. Due to the galvanically separated layers, the layer thickness distribution is physically predetermined and can hardly be influenced. After a certain operating time, the abutment surface widens in an undesirable manner due to wear, which results in changes in the pulling and falling times of the armature.

Advantages of the invention

The electromagnetically actuated valve according to the invention with the characterizing features of the main claim has the advantage over the fact that at least one of the abutting components is designed in such a way that the creation of a wear-resistant surface is ensured that the stop surface is not undesirably enlarged by wear even after a long period of operation, so that the pulling and falling times of the movable component remain almost constant. This is achieved in that at least one of the abutting components has a wedge-shaped surface before the wear resistance is generated. This wedge-shaped surface can be precisely adapted to different conditions to achieve a magnetic and hydraulic optimum.

The measures listed in the subclaims enable advantageous developments and improvements of the electromagnetically actuated valve, in particular fuel injection valve, specified in the main claim.

It is particularly advantageous to produce the extremely precise surface shape of at least one of the striking components mechanically using a ground countersinking tool. In this way, very precise dimensions can be achieved. With the aid of the very precisely ground tools, tighter manufacturing tolerances can be maintained than before, so that there is very little variation in the pull-in and, in particular, fall-out times of the armature during operation of the injection valve.

It is also advantageous that hydraulic bonding is completely excluded by means of a wedge-shaped anchor and / or core, since the wedge-shape remains in any case even with largely flat layers. The layers on at least one of the striking components have only a fraction of the wedge shape of the components themselves. The wedge-shaped surface shape of the at least one component, e.g. B. the anchor, it also allows that non-galvanic and magnetic wear-resistant layers can be applied without the requirement for a very small stop area remains unfulfilled.

A particular advantage is that the surface of at least one of the abutting components, in its highest area closest to the opposite component, is made wear-resistant by using a method known per se, e.g. a nitriding process such as plasma nitriding or gas nitriding etc. is hardened.

drawing

Exemplary embodiments of the invention are shown in simplified form in the drawing and are explained in more detail in the following description. FIG. 1 shows a fuel injection valve, FIG. 2 shows an enlarged stop of the

Injection valve in the area of the core and armature, FIG. 3 shows a first embodiment of a wedge armature designed according to the invention, FIG. 4 shows a second embodiment of a wedge armature and FIG. 5 shows a third embodiment of a wedge armature.

Description of the embodiments

The solenoid-operated valve shown in FIG. 1, for example, in the form of an injection valve for fuel injection systems of mixture-compressing, spark-ignited internal combustion engines has a core 2, which is surrounded by a solenoid coil 1 and serves as a fuel inlet connection and is, for example, tubular here and a constant over its entire length Has outer diameter. A coil body 3, which is stepped in the radial direction, takes up a winding of the magnetic coil 1 and, in conjunction with the core 2 having a constant outer diameter, enables a particularly compact structure of the injection valve in the area of the magnetic coil 1.

With a lower core end 9 of the core 2, a tubular metallic intermediate part 12 is connected, for example by welding, concentrically to a longitudinal valve axis 10 and thereby surrounds the core end 9 partially axially. The stepped coil body 3 partially overlaps the core 2 and, with a step 15 of larger diameter, the intermediate part 12 at least partially axially. A tubular valve seat carrier 16 extends downstream of the bobbin 3 and the intermediate part 12 and is, for example, firmly connected to the intermediate part 12. A longitudinal bore 17 runs in the valve seat support 16 and is formed concentrically to the valve longitudinal axis 10. Arranged in the longitudinal bore 17 is, for example, a tubular valve needle 19 which is connected at its downstream end 20 to a spherical valve closing body 21, on the periphery of which, for example, five flats 22 are provided for the fuel to flow past, for example by welding.

The injection valve is actuated electromagnetically in a known manner. The electromagnetic circuit with the magnet coil 1, the core 2 and an armature 27 is used for the axial movement of the valve needle 19 and thus for opening against the spring force of a return spring 25 or closing the injection valve. The armature 27 is connected to the End of the valve needle 19 facing away from the valve closing body 21 is connected by a first weld seam 28 and aligned with the core 2. In the downstream The end of the valve seat carrier 16 facing away from the core 2 is sealed in the longitudinal bore 17 by a cylindrical valve seat body 29, which has a fixed valve seat, by welding.

A guide opening 32 of the valve seat body 29 serves to guide the valve closing body 21 during the axial movement of the valve needle 19 with the armature 27 along the valve longitudinal axis 10. The spherical valve closing body 21 interacts with the valve seat of the valve seat body 29 which tapers in the direction of the cone in the direction of flow. On its end facing away from the valve closing body 21, the valve seat body 29 is connected concentrically and firmly to a spray-perforated disk 34, for example in the form of a pot. At least one runs in the base part of the spray perforated disk 34, for example four spray openings 39 formed by eroding or stamping.

The insertion depth of the valve seat body 29 with the cup-shaped spray perforated disk 34 determines the presetting of the stroke of the valve needle 19. The one end position of the valve needle 19 when the magnet coil 1 is not energized is determined by the valve closing body 21 resting on the valve seat of the valve seat body 29 , while the other end position of the valve needle 19 when the solenoid coil 1 is excited results from the contact of the armature 27 at the core end 9, that is to say precisely in the region which is embodied according to the invention and is characterized in more detail by a circle.

An adjusting sleeve 48, which is pushed into a flow bore 46 of the core 2 concentric to the longitudinal axis 10 of the valve and which is formed, for example, from rolled spring steel sheet, serves to adjust the spring preload on the adjusting sleeve 48 Return spring 25, which in turn is supported with its opposite side on the valve needle 19. The injection valve is largely enclosed with a plastic encapsulation 50, which extends from the core 2 in the axial direction via the magnet coil 1 to the valve seat support 16. This plastic encapsulation 50 includes, for example, an injection-molded electrical connector 52.

A fuel filter 61 projects into the flow bore 46 of the core 2 at its inlet end 55 and provides for the filtering out of those fuel components which, because of their size, could cause blockages or damage in the injection valve.

FIG. 2 shows the area of the one end position of the valve needle 19 marked with a circle in FIG. 1, in which the armature 27 strikes the core end 9 of the core 2, on a different scale. It is already known to apply metallic layers 65 to the core end 9 of the core 2 and to the armature 27, for example chrome or nickel layers, by means of electroplating. The layers 65 are applied both to an end face 67 running perpendicular to the longitudinal valve axis 10 and at least partially to a peripheral face 66 of the armature 27. These layers 65 are particularly wear-resistant and, with their small surface area, reduce hydraulic sticking of the striking surfaces, but without being able to reliably prevent it. The layer thickness of these layers 65 is generally between 10 and 25 μm.

For the function of the injection valve, it is necessary that the core 2 and armature 27 only in a relatively small area, for example only in the outer, from the valve. Strike the area of the upper end face of the anchor 27 facing away from the longitudinal axis 10. This requirement is met by the galvanic coating. In the case of galvanic coating, a field line concentration occurs at the edges of the parts to be coated, here core 2 and armature 27, which leads to a wedge-shaped layer thickness distribution, as indicated in FIG. 2. The wedge-shaped layer 65 applied is therefore only stressed in a small area during the operation of the injection valve. In continuous operation, however, there is no longer a defined stop surface, since parts of the layer 65 are removed by several million stops, so that the stop surface increases ever further and thus the wedge is continuously reduced.

In contrast, part of the armature 27 according to the invention is shown in the area of its upper end face 67 in FIG. 3, which has a wedge section 73 with an inclined, oblique course with respect to the valve longitudinal axis even before the coating or the creation of the wear resistance of the surface 10 has, so that the armature 27 has a wedge shape there. The inclination of the wedge section 73 of the end face 67 of the armature 27 extends inwards in the exemplary embodiment in FIG. 3, it also being possible for a wedge section 73 of the end face 67 to be inclined outward (FIG. 4). The wedge shape of the armature 27 in the region of the end face 67 is already produced during the mechanical processing, for example by means of a correspondingly ground countersinking tool.

While the layer thickness distribution that arises in the case of electrodeposited layers 65 is physically predetermined and can hardly be influenced, the wedge shape of the armature 27 before the coating or the generation of the wear resistance in accordance with the required values are predetermined and manufactured such that a magnetic and hydraulic optimum is achieved in each case when used. Hydraulic adhesion of the armature 27 to the core 2 is now completely ruled out by the wedge-shaped armature, since the wedge-shape is present in any case even in the case of layers 65 that are largely flat (also magnetic). With the help of very precisely ground countersinking tools, tighter manufacturing tolerances for the wedge can be maintained than before, so that there is even less variation in the pull-in and fall-out times of the armature 27 when the injection valve is operated. The inclined wedge section 73 of the end face 67 also allows non-galvanic, wear-resistant layers, which may also be magnetic, to be applied without the requirement for a very small stop area remaining unfulfilled.

In addition, the end face 67, at least in the region of its highest point, can be made wear-resistant by treating the surface by means of a hardening process. As a hardening process, e.g. the known nitriding processes such as plasma nitriding or gas nitriding are suitable.

In the exemplary embodiment according to FIG. 3, starting from the circumferential surface 66 of the armature 27, a stop section 68 of the end face 67 is initially provided, which extends radially inward over a width a perpendicular to the longitudinal valve axis 10 and serves as a stop surface. This

Stop section 68 represents an almost completely constant annular surface a over the entire operating time. The wear of the stop surface during continuous operation is thus precisely defined. In order to achieve a hydraulic and magnetic optimum, the is Wedge section 73 ideally inclined at an angle between> 0 ° and <= 1 ° with respect to stop section 68. The minimally wedge-shaped, e.g. B. made of chrome layer 65, which is deposited on the end face 67, has only a fraction of the inclination of the inclined wedge section 73 of the armature 27 adjoining the stop section 68. As a result, the coating remains on before coating Anchor 27 provided inclination of the wedge section 73 is completely preserved or is minimally reinforced.

Since the abutment surface width, which corresponds to the width a of the abutment section 68, remains constant even when worn, there is a constant contact width during the abutment of the core 2 and armature 27 over the entire

Lifetime available, whereby the hydraulic conditions in the gap between the core 2 and the armature 27 remain constant, which is a particular advantage. As already mentioned, at least the surface of the stop section 68 can also be made wear-resistant by a hardening process, so that no additional layer 65 has to be applied to the end face 67.

The same effects can also be achieved if both the armature 27 and the core 2 are provided with wedge sections 73 of the end faces 67 before the coating or the generation of a wear-resistant surface. This ensures an even higher level of security against the impact and prevents hydraulic gluing. If it is expedient, the wedge portion of the end face can of course also be attached only to the core 2, the armature 27 keeping, for example, a flat end face.

Further exemplary embodiments of embodiments designed according to the invention The anchors 27 are shown in FIGS. 4 and 5. An anchor 27 is shown in FIG. 4, in which the wedge section 73 of the end face 67 is designed inclined to the outside.

An exemplary embodiment of the armature 27 according to the invention, in which the end face 67 is formed only by the wedge section 73, is shown in FIG. 5. The stop section 68, which has at least a slight radial extension, is completely dispensed with here; rather, there is a wedge on the entire end face 67, so there is no area of the end face 67 perpendicular to the longitudinal axis 10 of the valve. Particularly at very small angles of the wedge section 73, there is also a stable stop, so that a defined stop surface remains even during continuous operation . In addition to the possibility shown in FIG. 5 of the course of the inclination of the wedge section 73 in the direction of the valve longitudinal axis 10, an exemplary embodiment analogous to the exemplary embodiment shown in FIG. 4, in which the wedge section is located, is also conceivable 73 extends in the direction away from the longitudinal axis 10 of the valve, that is to say is inclined outward.

Since the wedge section 73 already exists on at least one end face 67 of armature 27 and / or core 2, which was previously achieved only by applying chrome or nickel layers, as already mentioned, other methods for increasing quality by means of verbs can now also be used ¬ improvement of the wear resistance of the end face 67 are used. Through the use of hardening processes, e.g. Plasma nitriding, gas nitriding or carburizing, by means of which the surface structure on the armature 27 and / or core 2 is changed, methods for direct coating can even be dispensed with entirely.

Claims

claims

1. Electromagnetically actuated valve, in particular fuel injection valve for fuel injection systems of internal combustion engines, with a valve longitudinal axis, with a core made of ferromagnetic material, with a magnetic coil and with an armature which actuates a valve closing body interacting with a fixed valve seat and against a stop surface when the magnet coil is excited of the core, characterized in that at least one of the two end faces (67) of the components armature (27) and core (2), which are each directed towards the other opposite component, at least one to the valve longitudinal axis (10) oblique wedge section (73) sits.

2. Valve according to claim 1, characterized in that we at least one of the two end faces (67) of the components armature (27) and core (2) in a stop section (68) and the at least one wedge section extending obliquely to the valve longitudinal axis (10) (73) is divided and the at least one stop section (68) has a defined width (a).

3. Valve according to claim 2, characterized in that the at least one stop section (68) on armature (27) and / or the core (2) has a width (a) which represents only a fraction of the diameter of the end face (67).

4. Valve according to claim 1, characterized in that the at least one wedge section (73) extending obliquely to the longitudinal valve axis (10) extends over the entire end face (67).

5. Valve according to claim 2 or 4, characterized in that the at least one wedge portion (73) on the core (2) and / or armature (27) in the direction of the valve longitudinal axis (10) is inclined.

6. Valve according to claim 2 or 4, characterized in that the at least one wedge section (73) on the core (2) and / or armature (27) in the direction of the valve longitudinal axis (10) is inclined away.

7. Valve according to claim 1, characterized in that the core (2) and / or armature (27) in the region of the end face

(67) are coated.

8. Valve according to claim 7, characterized in that the layer (65) applied by the coating is magnetic.

9. Valve according to claim 1, characterized in that the core (2) and / or armature (27) in the region of the end face (67) are treated by means of a hardening process.