EP0683861A1

EP0683861A1 - Electromagnetic valve

Info

Publication number: EP0683861A1
Application number: EP95900659A
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: JPH08506876A; CZ284430B6; CZ198095A3; EP0683861B1; JP4755619B2; ES2113722T3; CN1116870A; BR9406081A; JP2007187167A; CN1055524C; RU2131992C1; WO1995016125A1

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 least one part, for example the armature (27) that has a stepped surface before the wear-resistant layer is applied. The stepped surface may be produced in a variable manner depending on the desired optimum magnetic and hydraulic properties. The ring-shaped bearing section (69) formed by the step has a defined bearing surface or contact width (b) 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, as a result of which the effects of residual magnetism on the moving parts of the fuel injector are minimized.

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 for those particularly stressed by wear and corrosion

Parts of an injection valve to use hard molybdenum layers 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 form 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 circumferential 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, a minimally thicker layer being achieved on the outer edges. Due to the galvanically deposited layers, the layer thickness distribution is physically predetermined and can hardly be influenced. After a certain operating time, the abutment surface widens undesirably due to wear, which results in changes in the armature's pull-in and fall-out times.

Advantages of the invention

The electromagnetically actuated valve according to the invention with the characterizing features of the main claim has the advantage that at least one of the abutting components is designed in such a way that after the creation of a wear-resistant surface it is ensured that the abutment surface even after a long period of operation is not undesirably increased by wear, so that the pulling and falling times of the movable component remain almost constant. That will achieved by at least one of the abutting components already having a stepped surface prior to the generation of the wear resistance. This stepped surface can be precisely adapted to different conditions to achieve a magnetic and hydraulic optimum.

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

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.

The stepped surface shape of the at least one component, eg. B. the armature, 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 the stop area of at least one of the abutting components is made wear-resistant by using a method known per se, e.g. B. a nitriding process such as plasma nitriding or gas nitriding or the like is hardened.

A small, ring-shaped and precisely defined stop area is provided if a step is advantageously introduced on at least one component surface serving as a stop. The ring-shaped stop region with a defined stop surface width, which corresponds to the contact width, remains constant over the entire service life, since wear of the stop surface during continuous operation by the step does not lead to an increase in the contact width. The impact security is fully guaranteed. Hydraulic gluing is impossible due to the small stop surface. Since a constant contact width is guaranteed over the entire service life, the hydraulic conditions in the gap between the striking parts, e.g. B. between core and anchor, constant.

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 region of the core and armature, FIG. 3 shows a first exemplary embodiment of an armature graded according to the invention, FIG. 4 shows a second exemplary embodiment of a stepped armature and FIG. 5 shows a third embodiment Example of a stepped anchor. Description of the embodiments

The electromagnetically actuated 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 magnetic coil 1 and serves as a fuel inlet connection and is, for example, tubular here and has a constant outer diameter over its entire length. A coil body 3, which is stepped in the radial direction, receives a winding of the magnetic coil 1 and, in conjunction with the core 2, which has a constant outer diameter, enables a particularly compact design of the injection valve in the area of the magnetic coil 1.

With a lower core end 9 of the core 2, a tubular metal intermediate part 12 is tightly connected concentrically to a longitudinal valve axis 10, for example by welding, and thereby partially axially surrounds the core end 9.

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, at its downstream end 20, has a spherical valve closing body 21, on the circumference of which, for example, five flats 22 are provided for the fuel to flow past, for example is connected 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 with the valve closing body 21 facing away from the end of the valve needle 19 by a first weld 28 and aligned to the core 2. In the downstream end of the valve seat carrier 16 facing away from the core 2, a cylindrical valve seat body 29, which has a fixed valve seat, is tightly mounted in the longitudinal bore 17 by welding.

A guide opening 32 of the valve seat body 29 is used 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 a truncated 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. Position of the valve needle 19 when the magnet coil 1 is not excited is determined by the contact of the valve closing body 21 on the valve seat of the valve seat body 29, while the other end position of the valve needle 19 when the magnet coil 1 is excited results from the contact of the armature 27 at the core end 9 , that is to say exactly in the area which is formed 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 concentrically 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 of the return spring 25 resting on the adjusting sleeve 48, which in turn is with its opposite side supported on the valve needle 19.

The injection valve is largely enclosed in a plastic encapsulation 50, which extends from the core 2 in the axial direction via the solenoid coil 1 to the valve seat carrier 16. About this plastic encapsulation

50 includes, for example, a molded-on 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. Already loaded it is 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 abutting surfaces, but without being able to reliably prevent it. The

Layer thickness of these layers 65 is generally between 10 and 25 microns.

For the function of the injection valve, it is necessary for core 2 and armature 27 to strike only in a relatively small area, for example only in the outer region of the upper end face of armature 27 facing away from valve longitudinal axis 10. This requirement is met by the galvanic coating. In the 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 ¬ occurs. 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 anchor 27 according to the invention is shown in the area of its upper end face 67 in FIG. 3, which already before the coating or the production. has a step section 70 due to the wear resistance of the surface.

While the layer thickness distribution that occurs in the case of electrodeposited layers 65 is physically predetermined and can hardly be influenced, the step of the anchor 27 before the coating or the generation of the wear resistance can be predetermined and manufactured in accordance with the required values so that a magnetic and hydraulic optimum is achieved in each case. With the help of very precisely ground countersinking tools, narrow manufacturing tolerances can be maintained for the step, so that there is an extremely small variation in the pull-in and drop-out times of the armature 27 when the injection valve is in operation. The step section 70 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 area of its stop section 69, 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.

The step section 70 in the upper end face 67 of the armature 27, which represents a depression as shown in FIG. The step section 70 has the consequence that the precisely defined annular stop section 69 is formed on the end face 67.

During continuous operation of the injection valve, several million stops from armature 27 on core 2 can take place. This in turn means that minimal wear on the abutment surface cannot be avoided. Through the step section 70, the stop section 69 of the upper end face 67 of the armature 27, which serves as a stop, now clearly protrudes over a step bottom 71. The protruding, ring-shaped stop section 69 with a width b between 20 and 500 μm thus serves as a stop, which in the embodiment according to FIG. 3 lies between the peripheral surface 66 and the step section 70, which is formed inwardly offset. This stop section 69 maintains a constant width b over the entire operating time. The abovementioned wear therefore no longer has any influence on the stop surface width or contact width. Hydraulic gluing is excluded due to the small stop surface. Since a constant contact width is guaranteed over the entire service life, the hydraulic conditions in the gap between the striking parts, here between core 2 and armature 27, remain a great advantage. Compared to the flat stop surface of the stop section 69, the advantages of the invention are obtained at an axial distance of 5 μm from the step floor 71. The hydraulic and magnetic optimum is achieved by a suitable choice of the width b and the depth of the step base 71, which is between 5 and 15 μm, for example.

It is also conceivable for both the armature 27 and the core 2 to be coated with a corresponding step before coating or generating a wear-resistant surface. section 70 are provided, so that very precisely defined annular stop sections 69 are formed on both abutting sides, as shown in FIG. In addition, it is possible to provide this step section 70 only on the core 2, while the armature 27 is given a flat end face, for example. These examples, not shown, will certainly not be used as often; However, the geometry of the step represents nothing other than the exemplary embodiment shown in FIG. 3 on the armature 27.

FIGS. 4 and 5 show further exemplary embodiments of anchors 27 designed according to the invention. It is conceivable that the stop section 69 is formed on the end face 67 towards the longitudinal axis 10 of the valve, while the step section 70 is offset axially outward toward the peripheral face 66 lies (Figure 4). FIG. 5 shows an exemplary embodiment of the armature 27, in which the stop section 69 is surrounded on the inside and outside, that is to say to the peripheral surface 66 and to the valve longitudinal axis 10, by step sections 70.

Since the step section 70 is already present on at least one end face 67 of the armature 27 and / or core 2, as already mentioned, the application of

Processes deviating from chromium or nickel layers are used to increase the quality by improving the wear resistance of the end face 67. Through the use of hardening processes, e.g. Plasma nitriding, gas nitriding or carburizing, by means of which the surface structure on the anchor 27 and / or core 2 is changed, can even be completely dispensed with methods for direct coating.

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 solenoid coil with an armature which actuates a valve closing body interacting with a fixed valve seat and against a stop surface when the solenoid 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, into a stop section (69) and at least one Compared to the stop section (69) recessed step section (70) and the at least one stop section (69) has a defined width (b).

2. Valve according to claim 1, characterized in that the at least one stop portion (69) on armature (27) and / or core (2) has a width (b) which represents only a fraction of the diameter of the end face (67).

3. Valve according to claim 2, characterized in that the at least one stop portion (69) on armature (27) and / or core (2) has a width (b) between 20 and 500 microns.

4. Valve according to claim 1, characterized in that the at least one step section (70) on the core (2) and / or armature (27) starting from the stop section

(69) extends in the direction of the valve longitudinal axis (10).

5. Valve according to claim 1, characterized in that the at least one step section (70) on the core (2) and / or armature (27) starting from the stop section (69) in the direction of the valve longitudinal axis (10) extends er¬ .

6. 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.

7. Valve according to claim 6, characterized in that the layer (65) applied by the coating is magnetic.

8. 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.