EP0683861B1 - Electromagnetic valve - Google Patents

Description

State of the art

The invention is based on an electromagnetically actuated Valve according to the genus of the main claim. It are already different electromagnetically operated Valves, in particular fuel injection valves, where wear-resistant components with wear-resistant Layers are provided.

From DE-OS 29 42 928 it is already known to be wear-resistant diamagnetic material layers on wear-stressed Parts such as anchors and nozzle body. These applied layers serve to limit the Stroke of the valve needle, reducing the effects of residual magnetism on the moving parts of the fuel injector be minimized.

From DE-OS 32 30 844 is also known anchor and Stop surface of a fuel injector with wear-resistant Surfaces. These surfaces can be nickel-plated, for example, with an additional one Be provided layer, or nitrided, that is Storage of nitrogen must be hardened.

It is also known from DE-OS 37 16 072 for particularly stressed by wear and corrosion Parts of an injector to use hard molybdenum layers who are thin and subsequently with Diamonds can be edited.

In DE-OS 38 10 826 is a fuel injector described, in which at least one stop surface spherical is designed to be extremely accurate To reach air gap, being centered on the stop surface a round body insert made of non-magnetic, high-strength Material is formed.

A fuel injector is also from EP-OS 0 536 773 known, at the anchor on its cylindrical Circumferential surface and an annular stop surface Hard metal layer is applied by electroplating. This layer of chrome or nickel has, for example a thickness of 15 to 25 µm. As a result of the galvanic coating there is a slight wedge-like layer thickness distribution, with a slightly thicker on the outer edges Layer is reached. By the galvanically separated Layers the layer thickness distribution is physical predefined and can hardly be influenced. After a certain period of operation the stop surface widens due to wear in an undesirable manner, causing changes result in the anchor'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 in contrast, the advantage that at least one of the other striking components is designed so that after ensures the creation of a wear-resistant surface is that the stop surface even after a long period of operation not through wear and tear in an undesirable manner is increased so that the pull-in and fall times of movable component remain almost constant. It will achieved that at least one of the striking Components before the wear resistance is created has a stepped surface. This stepped surface can be used to achieve a magnetic and hydraulic optimums to different ones Adjust conditions exactly.

By the measures listed in the subclaims are advantageous developments and improvements of specified in the main claim electromagnetically actuated Valve, in particular fuel injector possible.

It is particularly advantageous to have the extremely precise surface shape at least one of the striking components mechanically using a ground countersink tool. In this way, very precise dimensions can be achieved. With Using the very precisely ground tools can be tighter Manufacturing tolerances are adhered to so far, so that it to a very low level when operating the injector Scatter the suit and especially fall time of the Anchor is coming.

The stepped surface shape of the at least one component, e.g. B. the anchor, it also allows that also non-galvanic and magnetic wear-resistant layers can be applied without the need for a very small stroke area remains unfulfilled.

A particular advantage is that the surface of the stop area at least one of the abutting ones Making components wear-resistant, that they by means of a known method, for. B. a nitriding process such as plasma nitriding or gas nitriding or similar is hardened.

A small, ring-shaped and precisely defined in size Stop area is given if more advantageous Way on at least one serving as a stop Component surface is introduced a step. The thus ring-shaped stop area with a defined stop surface width, that corresponds to the contact width, namely remains constant over the entire service life, because a wear of the contact surface during continuous operation by the Level does not lead to an increase in the contact width. The impact security is fully guaranteed. A hydraulic gluing is due to the small stop area locked out. Because over the entire life constant contact width is guaranteed to remain as a great advantage the hydraulic conditions in the gap between the striking parts, e.g. B. between core and Anchor, constant.

drawing

Embodiments of the invention are in the drawing shown in simplified form and in the description below explained in more detail. 1 shows a fuel injector, Figure 2 shows an enlarged stop of the Injector in the area of the core and armature, Figure 3 a first embodiment of a stepped according to the invention Ankers, Figure 4 shows a second embodiment a stepped anchor and Figure 5 shows a third embodiment of a tiered anchor.

Description of the embodiments

The electromagnetic shown in Figure 1, for example actuatable valve in the form of an injection valve for fuel injection systems of mixture compression, spark-ignited internal combustion engines has one of a magnetic coil 1 surrounding, as a fuel inlet connector serving core 2, which for example is tubular here and is constant over its entire length Has outer diameter. One in the radial direction stepped bobbin 3 takes a winding of the solenoid 1 and in conjunction with one constant core 2 having a special compact design of the injection valve in the area the solenoid 1.

With a lower core end 9 of the core 2 is concentric to a valve longitudinal axis 10 tightly a tubular metal Intermediate part 12 connected for example by welding and partially surrounds the core end 9 axially. The stepped bobbin 3 partially overlaps the core 2 and with a step 15 of larger diameter the intermediate part 12 at least partially axially. Downstream of the Coil body 3 and the intermediate part 12 extends a tubular valve seat support 16, for example is firmly connected to the intermediate part 12. In the valve seat carrier 16 runs a longitudinal bore 17 which is concentric to the valve longitudinal axis 10 is formed. In the longitudinal bore 17 is a tubular valve needle, for example 19 arranged at its downstream end 20 with a spherical valve closing body 21 the extent of which, for example, five flattenings 22 Flowing past the fuel are provided, for example is connected by welding.

The injection valve is actuated in a known manner Way electromagnetic. For axial movement of the valve needle 19 and thus to open against the spring force of one Return spring 25 or closing of the injection valve serves the electromagnetic circuit with the magnetic coil 1, the core 2 and an anchor 27. The anchor 27 is with the the valve closing body 21 facing away from the end of the valve needle 19 connected by a first weld 28 and on the core 2 aligned. In the downstream, the Core 2 facing away from the end of the valve seat support 16 is in the Longitudinal bore 17 a cylindrical valve seat body 29, which has a fixed valve seat, by welding tightly assembled.

For guiding the valve closing body 21 during the axial movement the valve needle 19 with the armature 27 along the Longitudinal valve axis 10 serves a guide opening 32 of the valve seat body 29. The spherical valve closing body 21 acts with the shape of a truncated cone in the direction of flow tapered valve seat of the valve seat body 29 together. On its end facing away from the valve closing body 21 is the valve seat body 29 with, for example Pot-shaped spray plate 34 concentrically and firm, connected. In the bottom part of the spray plate 34 runs at least one, for example run four formed by eroding or stamping Spray openings 39.

The insertion depth of the valve seat body 29 with the pot-shaped spray disk 34 determines the default setting of the stroke of the valve needle 19. Here is the one end position the valve needle 19 when the solenoid is not energized 1 by the installation of the valve closing body 21 on the valve seat of the valve seat body 29 set while the other end position of the valve needle 19 when the solenoid coil is energized 1 results from the installation of the armature 27 at the core end 9, So exactly in the area that is designed according to the invention and is identified by a circle.

One in a concentric to the longitudinal axis 10 of the valve Flow bore 46 of the core 2 inserted adjusting sleeve 48, for example made of rolled spring steel sheet is formed, used to adjust the spring preload the adjoining the adjusting sleeve 48 Return spring 25, which in turn is with its opposite Supported on the valve needle 19.

The injection valve is largely with a plastic coating 50 enclosed, starting from the core 2 in axial direction via the solenoid coil 1 to the valve seat support 16 extends. About this plastic encapsulation 50 belongs, for example, to a co-molded electric Connector 52.

A fuel filter 61 projects into the flow bore 46 of the Core 2 at its inlet end 55 and provides for filtering out such fuel components, which due to their size in the injector blockages or cause damage.

In FIG. 2, the one marked with a circle in FIG. 1 is shown Range of one end position of the valve needle 19, in which the armature 27 strikes the core end 9 of the core 2, shown on a different scale. Already known is the application of metallic layers 65 the core end 9 of the core 2 and on the anchor 27, for example of chrome or nickel layers, by means of electroplating. The layers 65 are both on a End face extending perpendicular to the valve along the longitudinal axis 10 67 and at least partially on a peripheral surface 66 the anchor 27 applied. These layers are 65 particularly wear-resistant and reduce with their small size Surface a hydraulic gluing of the striking surfaces, but without being able to prevent it safely. 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 core 2 and anchor 27 only in a relatively small area, for example only in the outer, from the valve longitudinal axis 10 facing away from the upper face of the Strike anchor 27. This demand is being followed through reached the electroplating. With the galvanic Coating occurs on the edges of the surface to be coated Parts, here core 2 and anchor 27, a field line concentration which leads to a wedge-shaped layer thickness distribution, as indicated in Figure 2 occurs. The wedge-shaped layer 65 applied is thus at Injector operation only in a small area claimed. However, there is no longer any continuous operation a defined stop surface because of several million Stops parts of layer 65 are removed, so that the stop surface increases and thus the wedge is continuously reduced. In contrast, part of the invention is shown in Figure 3 Anchor 27 in the area of its upper end face 67 shown that before coating or generating the wear resistance of the surface a step section 70 has.

While the layers 65 resulting layer thickness distribution is physically predetermined and can hardly be influenced, the level of the anchor can 27 before coating or generating wear resistance predetermined in accordance with the required values and be made that when used each achieved a magnetic and hydraulic optimum becomes. With the help of very precisely ground countersinking tools can maintain tight manufacturing tolerances for the stage be so that when the injector operates an extremely low spread of the pull-in and fall times of the anchor 27 comes. The step portion 70 of the end face 67 also allows non-galvanic, wear-resistant Layers, which may also be magnetic, can be applied without the need for a very small stroke area remains unfulfilled.

In addition, the end face 67, at least in the area of it Stop portion 69, by treating the surface made wear-resistant by means of a hardening process will. As a hardening process, e.g. the well-known Nitriding processes such as plasma nitriding or gas nitriding suitable.

With the step section 70 in the upper end face 67 of the armature 27, which, as shown in FIG. 3, has a depression represents, the highest security is an over the entire life of the injector is constant permanent stop surface width and thus contact width given. The step section 70 has the consequence that the exact Defined annular stop portion 69 on the End face 67 is formed.

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, annular stop section 69 with a width b of between 20 and 500 μm thus serves as a stop, which in the exemplary embodiment according to FIG. 3 lies between the peripheral surface 66 and the stepped section 70 which is formed inwards. 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 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, 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 even at an axial distance of 5 μm from the step base 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, for example, between 5 and 15 μm.
It is also conceivable that both the armature 27 and the core 2 are provided with a corresponding step section 70 prior to coating or producing a wear-resistant surface, so that very precisely defined annular stop sections 69 are formed on both abutting sides, such as it shows the figure 3. 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 does not represent anything other than the embodiment shown in FIG. 3 on the armature 27.

Further exemplary embodiments of those designed according to the invention Anchors 27 are shown in FIGS. 4 and 5. It is so conceivable that the stop portion 69 to the valve longitudinal axis 10 is formed on the end face 67, during the Step portion 70 axially offset outward to the peripheral surface 66 lies (Figure 4). An exemplary embodiment is shown in FIG of the anchor 27 shown, in which the Stop section 69 inside and outside, that is to the peripheral surface 66 and towards the valve longitudinal axis 10, from section sections 70 is surrounded.

Since at least one end face 67 of armature 27 and / or core 2, step section 70 already exists, can, as already mentioned, also from the application of Chrome or nickel layers deviating processes to increase quality by improving wear resistance the end face 67 are used. Because of the engagement hardening processes, e.g. Plasma nitriding, gas nitriding or carburizing, through which the surface structure on the anchor 27 and / or core 2 is changed, can even be entirely on Processes for immediate coating can be dispensed with.

Claims (8)

1. Electromagnetically operable valve, in particular a fuel injection valve for fuel-injection systems of combustion engines, having a valve longitudinal axis, having a core made from ferromagnetic material, having a magnet coil, and having an armature which actuates a valve-closing body interacting with a fixed valve seat and, when the magnet coil is excited, is drawn against an impact face of the core, characterized in that at least one of the two end faces (67) of the component parts armature (27) and core (2), which are respectively directed towards the other opposing component part, is divided up into an impact segment (69) and at least one step segment (70), which is depressed relative to the impact segment (69), and the at least one impact segment (69) has a defined width (b).
2. Valve according to Claim 1, characterized in that the at least one impact segment (69) on the armature (27) and/or core (2) possesses a width (b) representing only a fraction of the diameter of the end face (67).
3. Valve according to Claim 2, characterized in that the at least one impact segment (69) on the armature (27) and/or core (2) possesses a width (b) between 20 and 500 µm.
4. Valve according to Claim 1, characterized in that the at least one step segment (70) on the core (2) and/or armature (27), originating from the impact segment (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 segment (70) on the core (2) and/or armature (27), originating from the impact segment (69), extends in the direction away from the valve longitudinal axis (10).
6. Valve according to Claim 1, characterized in that the core (2) and/or armature (27) are coated in the region of the end face (67).
7. Valve according to Claim 6, characterized in that the coating (65) applied by the coating procedure is magnetic.
8. Valve according to Claim 1, characterized in that the core (2) and/or armature (27) are treated in the region of the end face (67) by means of a hardening process.

Images