DE102021213142A1 - Electromagnetically operable device and method of manufacturing a magnetic circuit component of an electromagnetically operable device - Google Patents

Abstract

An electromagnetically actuable device has an electromagnetic magnetic circuit with a magnetic coil (10), a movable magnetic circuit component (20) and/or at least one magnetic circuit component (13) fixed to the housing. According to the invention, a magnetic steel made of an iron-silicon material (FeSi) is used for the movable magnetic circuit component (20) and/or the at least one magnetic circuit component (13) fixed to the housing, the inner (40) and outer contour (41) of the respective magnetic circuit component ( 13, 20) are chromed on the surface for corrosion protection reasons.

Description

State of the art

The invention is based on an electromagnetically operable valve according to the species of the main claim.

From the DE 33 05 039 A1 an electromagnetically actuable valve in the form of a fuel injection valve is already known, which includes a valve housing and a core made of ferromagnetic material serving as an inner pole, as well as an axially movable armature that actuates a valve part that interacts with a fixed valve seat. When the solenoid coil is energized, the armature is pulled against a stop surface on the lower face of the valve body. The stop surface is delimited on the one hand by an inner bore of the valve housing and on the other hand by the edge of a groove which is formed in the end face of the valve housing. The circumference of the armature partially covers the groove.

From the EP 0 683 861 B1 an electromagnetically actuable valve in the form of a fuel injection valve for fuel injection systems of internal combustion engines is also already known, which has, among other things, a core made of ferromagnetic material serving as the inner pole, a magnet coil and an axially movable armature which actuates a valve closing body which interacts with a fixed valve seat and when the magnet coil is energized is pulled against an abutment surface of the core. At least one of the two end faces of the armature and core components, which are each directed towards the other opposing component, is divided into a stop section and at least one step section which is recessed in relation to the stop section. The stop section has a precisely defined width.

For high-performance magnetic circuits of various electromagnetically operated devices such as valves, pumps, actuators, switches, high-performance magnetic materials made of iron-cobalt (FeCo) with a certain proportion of cobalt are used as corrosion protection, such as FeCo49 with a 49% proportion of cobalt. Cobalt is one of the rare elements with a frequency of only 0.004% in the earth's crust. In addition, it is almost exclusively found in ores of other metals and has to be extracted in a complex manner, under poor working and environmental conditions in African or Latin American countries. Due to the importance of cobalt in the manufacture of electronic devices, there is likely to be a shortage in the supply of cobalt in the coming years. It is therefore desirable to replace cobalt in high-performance magnetic circuits with more easily obtainable and available elements and materials derived from them.

Advantages of the Invention

The electromagnetically actuable device according to the invention with the features of claim 1 has the advantage that galvanic hard chrome plating for FeSi components, which must be used for magnetic circuit components as the conventional proven manufacturing method for producing sufficient wear protection, is omitted. By doing without hard chrome, there are considerable advantages in terms of costs and environmental protection requirements.

For high-performance magnetic circuits, high-performance magnetic materials made of iron-cobalt (FeCo) with a certain proportion of cobalt are used as corrosion protection for various electromagnetically operated devices such as valves, pumps, actuators, switches, such as FeCo49 with a 49% proportion of cobalt. According to the invention, the rare element cobalt, which is difficult to obtain, can also be dispensed with.

In order to achieve adequate protection against corrosion, a known magnet steel made of an iron-silicon material (FeSi) and having sufficiently good magnetic properties is advantageously used for at least one magnetic circuit component of the electromagnetically actuated device, the inner and outer contour of which is chromium-plated throughout on the surface are.

Advantageous developments and improvements of the device specified in claim 1 or of the valve specified in claim 5 are possible as a result of the measures listed in the subclaims.

It is particularly advantageous to use the invention in an electromagnetically actuated valve, in particular a fuel injection valve for fuel injection systems of internal combustion engines, in which the movable armature and/or the inner pole fixed to the housing are then made wear-resistant and corrosion-resistant by chroming.

character list

• 1 einen axialen Schnitt durch ein Brennstoffeinspritzventil als Beispiel für ein elektromagnetisch betätigbares Ventil gemäß dem Stand der Technik,
• 2 eine vergrößerte Perspektivansicht auf eine Nadelbaugruppe mit einem frei bewegbaren Anker eines elektromagnetisch betätigbaren Ventils in Form eines Brennstoffeinspritzventils und
• 3 einen Längsschnitt durch einen Anker gemäß 2 mit angedeuteten inchromierten Oberflächen.

Exemplary embodiments of the invention are shown in simplified form in the drawing and explained in more detail in the following description. Show it

• 1 an axial section through a fuel injector as an example of an electric magnetically actuated valve according to the prior art,
• 2 an enlarged perspective view of a needle assembly with a freely movable armature of an electromagnetically actuated valve in the form of a fuel injector and
• 3 according to a longitudinal section through an anchor 2 with indicated chromed surfaces.

Description of the exemplary embodiments

Before using the 2 and 3 Exemplary embodiments of electromagnetically actuable devices according to the invention, in particular valves in the area of their magnetic circuit components, are to be described in more detail for a better understanding of the invention, first with reference to FIG 1 an already known fuel injection valve will be explained briefly with regard to its essential components.

This in 1 Fuel injection valve 1 shown is in the form of a fuel injection valve 1 for fuel injection systems of mixture-compressing, spark-ignited internal combustion engines. Fuel injector 1 is particularly suitable for injecting fuel directly into a combustion chamber (not shown) of an internal combustion engine.

However, the invention is in no way limited to fuel injection valves; however, fuel injectors of this type represent a preferred area of application of the invention. The invention can also be implemented on other electromagnetically actuated devices, such as other electromagnetically actuated valves other than fuel injectors (e.g. test bench valves or ABS valves), but also pumps, actuators, switches, etc. where high-performance magnetic materials are to be used in electromagnetic circuits.

The fuel injector 1 shown consists of a nozzle body 2 in which a valve needle 3 is arranged. The valve needle 3 is in operative connection with a valve closing body 4 which cooperates with a valve seat surface 6 arranged on a valve seat body 5 to form a sealing seat. In the exemplary embodiment, fuel injector 1 is a fuel injector 1 that opens inwards and has at least one spray-discharge opening 7 . The nozzle body 2 is sealed against an outer pole 9 of a magnetic coil 10 by a seal 8 . The magnet coil 10 is encapsulated in a coil housing 11 and wound onto a coil carrier 12 which bears against an inner pole 13 of the magnet coil 10 . The inner pole 13 and the outer pole 9 are separated from each other by a constriction 26 and connected to each other by a non-ferromagnetic connecting member 29 . The magnetic coil 10 is excited via a line 19 by an electrical current that can be supplied via an electrical plug contact 17 . The plug contact 17 is surrounded by a plastic casing 18 which can be injection molded onto the inner pole 13 .

The valve needle 3 is guided in a valve needle guide 14 which is disk-shaped. A paired shim 15 is used to adjust the stroke. An armature 20 is located upstream of the shim 15. This is non-positively connected via a first flange 21 to the valve needle 3, which is connected to the first flange 21 by a weld seam 22. A restoring spring 23 is supported on first flange 21 and is pretensioned by an adjusting sleeve 24 in the present design of fuel injector 1 .

Fuel channels 30, 31 and 32 run in the upper valve needle guide 14, in the armature 20 and on a lower guide element 36. The fuel is supplied via a central fuel supply 16 and filtered by a filter element 25. Fuel injection valve 1 is sealed by a seal 28 against a fuel distribution line (not shown) and by a further seal 37 against a cylinder head (not shown).

An annular damping element 33, which consists of an elastomer material, is arranged on the side of the armature 20 on the spray-discharge side. It rests on a second flange 34 which is non-positively connected to the valve needle 3 via a weld seam 35 . The damping element 33 serves to debounce the valve when the armature 20 strikes the lower flange 34, which thus indirectly forms a stop element.

A pre-stroke spring 38 is arranged between first flange 21 and armature 20 and holds armature 20 in contact with second flange 34 indirectly via damping element 33 when fuel injector 1 is in the idle state. The spring constant of the pre-stroke spring 38 is significantly smaller than the spring constant of the return spring 23.

When fuel injector 1 is at rest, armature 20 is acted upon by restoring spring 23 and pre-stroke spring 38 counter to its stroke direction in such a way that valve-closing body 4 is held in sealing contact with valve seat surface 6 . When the magnet coil 10 is energized, it builds up a magnetic field which initially de-energizes the armature 20 moves against the spring force of the pre-stroke spring 38 in the stroke direction, with an armature free travel being predetermined by the distance between the first flange 21 and the armature 20 . After passing through the free travel of the armature, the armature 20 also takes along the first flange 21, which is welded to the valve needle 3, against the spring force of the restoring spring 23 in the stroke direction. The armature 20 runs through a total stroke that corresponds to the height of the working gap 27 between the armature 20 and the inner pole 13 . The valve closing body 4 connected to the valve needle 3 lifts off the valve seat surface 6 and the fuel guided via the fuel channels 30 to 32 is sprayed off through the spray-discharge opening 7 .

If the coil current is switched off, the armature 20 falls off the inner pole 13 after the magnetic field has sufficiently decayed due to the pressure of the return spring 23, as a result of which the first flange 21 connected to the valve needle 3 moves in the opposite direction to the stroke direction. As a result, valve needle 3 is moved in the same direction, as a result of which valve closing body 4 touches valve seat surface 6 and fuel injector 1 is closed. The pre-stroke spring 38 then acts on the armature 20 in such a way that it does not bounce back from the second flange 34 but returns to the resting state without a stop bounce.

2 shows an enlarged perspective view of a needle assembly with a freely movable armature 20 of an electromagnetically actuated valve in the form of a fuel injector 1. According to the invention, the inner pole 13 is used for the movable magnetic circuit component, here the armature 20 and/or for the at least one magnetic circuit component fixed to the housing, in fuel injector 1 a magnetic steel made of an iron-silicon material (FeSi) is used, so that a steel containing cobalt (FeCo) can advantageously be dispensed with. In a particularly advantageous manner, the magnetic steel, which has a tendency to corrode and is made of an iron-silicon material (FeSi), is chrome-plated along its inner contour 40 and outer contour 41 on the surface.

3 shows a longitudinal section through an anchor 20 according to FIG 2 with indicated chromed surfaces along its inner contour 40 and outer contour 41. The inner contour 40 is formed by the openings and bores, such as the fuel channels 30 or the inner passage opening for the valve needle 3.

Advantageously, galvanic hard chromium plating, which must be used for armature 20 and inner pole 13 as the conventional, proven manufacturing method for producing adequate wear protection, is no longer required for FeSi components. By doing without hard chrome, there are considerable advantages in terms of costs and environmental protection requirements.

For high-performance magnetic circuits, high-performance magnetic materials made of iron-cobalt (FeCo) with a certain proportion of cobalt are used as corrosion protection for various electromagnetically operated devices such as valves, pumps, actuators, switches, such as FeCo49 with a 49% proportion of cobalt.

According to the invention, a solution is proposed that dispenses with both a cobalt-containing magnetic material and hard chrome plating with an FeSi material. Rather, the desired magnetic circuit components such as armature 20 and/or inner pole 13 are provided with corrosion and wear protection by chroming an FeSi component. Correspondingly suitable FeSi materials are known, for example, under the material numbers 1.3840, 1.3843, 1.3845 or 1.0884. These magnetic materials contain approximately 2.5 to 4% silicon, in particular approximately 3% silicon, and traces of sulfur and phosphorus.

Chrome plating is a manufacturing process to increase the corrosion resistance and wear resistance of metallic components. When chroming, the material is heated with chrome dispensers. In the process, elementary chromium diffuses thermochemically at temperatures of 1000°C to 1200°C into the surface of the respective component and forms a chromium-rich layer in the edge zone of the workpiece. Chromed steels are resistant to high temperatures. In the case of the magnetic circuit components to be chromized here, the chromium should ideally diffuse to a depth of 5 to 10 µm in the edge zone of the workpiece; but it can also make sense to allow the chromium to diffuse down to a depth of 20 to 50 µm.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 3305039 A1 [0002]
• EP 0683861 B1 [0003]

Claims (11)

Electromagnetically actuatable device with an electromagnetic magnetic circuit with a magnetic coil (10), a movable magnetic circuit component (20) and/or at least one magnetic circuit component (13) fixed to the housing, characterized in that for the movable magnetic circuit component (20) and/or the at least one magnetic circuit component fixed to the housing (13) a magnetic steel made of an iron-silicon material (FeSi) is used and the inner (40) and outer contour (41) of the respective magnetic circuit component (13, 20) are chrome-plated on the surface. Electromagnetically actuable device claim 1 , characterized in that the iron-silicon material (FeSi) for the magnetic circuit component (13, 20) has a proportion of approximately 2.5 to 4% silicon, in particular approximately 3% silicon, and traces of sulfur and phosphorus. Electromagnetically actuable device claim 1 or 2 , characterized in that elementary chromium is thermochemically diffused along the inner (40) and outer contour (41) of the respective magnetic circuit component (13, 20) from the surface. Electromagnetically actuable device claim 3 , characterized in that the chromized magnetic circuit component (13, 20) has a chromium-rich layer in the edge zone of the workpiece, which extends to a depth of 5 to 10 µm from the surface of the magnetic circuit component (13, 30). Electromagnetically actuable valve, in particular fuel injection valve for fuel injection systems of internal combustion engines, with an electromagnetic magnetic circuit with a magnetic coil (10), a movable armature (20) and an inner pole (13) fixed to the housing, characterized in that for the armature (20) and/or the inner pole (13) fixed to the housing, a magnetic steel made of an iron-silicon material (FeSi) is used and the inner and outer contour of the armature (20) and/or the inner pole (13) are chrome-plated on the surface. Electromagnetically operated valve claim 5 , characterized in that the iron-silicon material (FeSi) for the armature (20) and / or the inner pole (13) has a proportion of about 2.5 to 4% silicon, in particular about 3% silicon, and traces of sulfur and phosphorus. Electromagnetically operated valve claim 5 or 6 , characterized in that elementary chromium is thermochemically diffused along the inner (40) and outer contour (41) of the armature (20) and/or the inner pole (13) from the surface. Electromagnetically operated valve claim 7 , characterized in that the chromized armature (20) and/or the chromized inner pole (13) have a chromium-rich layer in the edge zone of the workpiece, which extends to a depth of 5 to 10 µm from the surface of the magnetic circuit component (13, 30). . A method of manufacturing a magnetic circuit component of an electromagnetically operable device according to any one of Claims 1 until 4 and Method for producing a magnetic circuit component of an electromagnetically actuated valve according to one of Claims 5 until 8th , characterized in that a magnetic steel made of an iron-silicon material (FeSi) is used for the magnetic circuit component (13, 20) and the inner (40) and outer contour (41) of the respective magnetic circuit component (13, 20) on the surface is chromed. Method of manufacturing a magnetic circuit component claim 9 , characterized in that elementary chromium diffuses thermochemically at temperatures of 1000°C to 1200°C into the surface of the respective magnetic circuit component (13, 20) and forms a chromium-rich layer in the edge zone of the workpiece. Method of manufacturing a magnetic circuit component claim 10 , characterized in that the chroming to form a chromium-rich layer in the edge zone of the workpiece is carried out to a depth of 5 to 10 µm from the surface of the magnetic circuit component (13, 30).

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