EP0683862B1 - 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 is designed to be extremely spherical to achieve an exact air gap, 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 results in a slightly wedge-shaped layer thickness distribution, being minimal on the outer edges thicker layer is reached. By the galvanically separated Layers the layer thickness distribution is physical predefined and can hardly be influenced. After a certain Operating time widens the stop surface due to wear and tear in an undesirable manner, causing Changes in anchor pull-in and drop-out times result.

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 a wear-resistant surface has been produced, it is ensured that the stop surface is not undesirably worn even after a long period of operation is increased 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 circumstances in order 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 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.

It is also advantageous that a wedge anchor and / or core hydraulic adhesion completely excluded is there, even with largely flat ones Layers the wedge is definitely present. The layers on at least one of the striking components have only a fraction of the wedge of the components themselves.

The wedge-shaped 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 in a very small impact area remains unfulfilled.

A particular advantage is that the surface in its highest, closest to the opposite component Area of at least one of the abutting ones Components are made wear-resistant in that using a method known per se, e.g. one Nitriding processes such as plasma nitriding or gas nitriding or similar is hardened.

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 an inventive wedge-shaped anchor, Figure 4 shows a second embodiment a wedge anchor and Figure 5 a third Embodiment of a wedge 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 Magnet coil 1 and in connection with the a core 2 having a constant outer diameter a particularly compact design of the injection valve in the Magnetic coil area 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 a return spring 25 or closing 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 end of the valve needle facing away from the valve closing body 21 19 connected by a first weld 28 and aligned to core 2. In the downstream The end of the valve seat carrier 16 facing away from the core 2 is shown in FIG the longitudinal bore 17 is 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 shaped, is used to adjust the Spring preload of 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 at the core end 9 of the core 2 strikes, shown on a different scale. Already it is known to apply metallic layers 65 on 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 perpendicular to the longitudinal axis 10 of the valve 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 area of the upper end face facing away anchor 27. This demand is just now achieved by the galvanic coating. With the galvanic Coating occurs at the edges of the coating parts, here core 2 and anchor 27, a field line concentration on, which leads to a wedge Layer thickness distribution, as indicated in Figure 2 is occurs. The wedge-shaped layer 65 applied So when operating the injector only in a small one Area occupied. However, in continuous operation no longer a defined stop surface because parts of layer 65 removed by several million attacks be so that the stop surface always further increases and thus the wedge is constantly increasing is 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 wedge section 73 with an inclined, oblique course opposite the valve longitudinal axis 10, so that the armature 27 there has a wedge shape. The inclination of the wedge section 73 of the End face 67 of armature 27 extends in the exemplary embodiment in Figure 3 inside, including a wedge section 73 of the end face 67 is inclined to the outside can be (Figure 4). The wedge shape of the anchor 27 in The area of the end face 67 is already in the mechanical Editing, for example by a corresponding ground countersinking tool.

While the layers 65 resulting layer thickness distribution is physically predetermined and can hardly be influenced, the wedge of the Anchor 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. Hydraulic bonding of the armature 27 to the core 2 is now completely excluded by the wedge anchor, because even with largely flat (also magnetic) Layers 65 definitely have the wedge is. With the help of very precisely ground countersinking tools can have tighter manufacturing tolerances for the wedge than have been observed so far, so that it is in operation of the injection valve to an even smaller spread of suit and fall time of the anchor 27 comes. The inclined one Wedge section 73 of the end face 67 also allows that also non-galvanic, wear-resistant layers that too may be magnetic, can be applied without that the requirement for a very small stop area remains unfulfilled.

In addition, the end face 67, at least in the area at its highest point, 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.

In the embodiment of Figure 3 is based on the peripheral surface 66 of the armature 27 is initially a stop section 68 of the end face 67 is provided, which over a width a radially inwards perpendicular to the longitudinal axis of the valve 10 extends and serves as a stop surface. This Stop section 68 represents the entire operating time an almost completely constant in width a Annular surface. The abutment surface wear at Continuous operation is precisely defined. To be a hydraulic and to achieve the magnetic optimum is Wedge section 73 ideally by an angle between> 0 ° and <= 1 ° inclined with respect to the stop section 68. The minimally wedge-shaped, e.g. B. made of chrome layer 65, the is deposited on the end face 67, only has a fraction of the slope of the abutting portion 68 inclined wedge section adjoining the inside 73 of anchor 27. Consequently, that remains before Coating provided on the armature 27 inclination of the wedge section 73 completely preserved or minimally reinforced.

Since the stop surface width is that of the width a of the stop section 68 corresponds, constant even with wear remains, is a constant contact width during the Striking core 2 and anchor 27 over the entire Lifespan available, which also affects 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 also wear-resistant thanks to a hardening process be made so that no additional Layer 65 must be applied to the end face 67.

The same effects can also be achieved if both the anchor 27 as well as the core 2 before coating or creating a wear-resistant surface with wedge sections 73 of the end faces 67 are provided. In order to can an even higher security against impact or prevention of hydraulic gluing can be guaranteed. If it is appropriate, of course, the attachment of a wedge section of the end face only on the core 2 be made, the anchor 27, for example, a flat end face.

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

An embodiment of the armature 27 according to the invention, in which the end face 67 only through the wedge section 73 is shown, Figure 5. This is completely on the one with at least a small radial extension Stop section 68 omitted; rather there is one Wedge on the entire face 67 before, there is So no longitudinal axis 10 perpendicular to the valve Area of the end face 67. Especially for very small ones Angles of the wedge section 73 are then more stable Stop before, so that even in continuous operation a defined The stop surface remains. In addition to the possibility shown in Figure 5 the slope of the wedge portion 73 in Direction to the valve longitudinal axis 10 is also an embodiment analogous to that shown in FIG. 4 Embodiment conceivable in which the wedge section 73 extends in the direction away from the valve longitudinal axis 10, is designed inclined outwards.

Since at least one end face 67 of armature 27 and / or core 2 already has the wedge section 73 which so far only through the application of chrome or nickel layers has been achieved, as already mentioned, other methods of increasing quality through improvement the wear resistance of the end face 67 to Come into play. Through the use of hardening processes, such as e.g. Plasma nitriding, gas nitriding or carburizing the surface structure on anchor 27 and / or core 2 is changed, can even be entirely based on procedures for immediate Coating can be dispensed with.

Claims (9)

1. Electromagnetically operable valve, in particular a fuel injection valve for fuel injection systems of internal-combustion engines, having a valve longitudinal axis, having a core made from ferromagnetic material, having a magnet coil, and an armature, which operates a valve closing member cooperating with a fixed valve seat and is drawn against a stop surface of the core when the magnet coil is excited, characterized in that at least one of the two end faces (67) of the components of armature (27) and core (2), which are each directed towards the other, opposite component, has at least one wedge section (73) extending obliquely relative to the valve longitudinal axis (10).
2. Valve according to Claim 1, characterized in that at least one of the two end faces (67) of the components of armature (27) and core (2) is divided into a stop section (68) and the at least one wedge section (73) extending obliquely relative to the valve longitudinal axis (10), 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 the armature (27) and/or 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 relative to the valve longitudinal 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 section (73) on the core (2) and/or armature (27) extends in an inclined fashion in the direction of the valve longitudinal axis (10).
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) extends in an inclined fashion away from the valve longitudinal axis (10).
7. 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).
8. Valve according to Claim 7, characterized in that the layer (65) applied by coating is magnetic.
9. 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.

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