EP2097913B1 - Method for producing a static magnetic circuit component - Google Patents

Description

State of the art

The invention is based on a method for producing a fixed magnetic circuit component according to the preamble of the main claim.

In the FIG. 1 a known fuel injection valve of the prior art is shown, which has a classic three-part construction of an inner metal flow guide member and at the same time housing component. This inner valve tube is formed from an inlet port forming an inner pole, a nonmagnetic intermediate part and a valve seat carrier receiving a valve seat, and in the description FIG. 1 explained in more detail.

From the DE 35 02 287 A1 is already a method for producing a hollow cylindrical metal housing with two magnetizable housing parts and an intermediate, the housing parts magnetically separating, non-magnetic housing zone known. This metal housing is in this case prefabricated from a magnetizable blank in one piece to an oversize in the outer diameter, wherein in the inner wall of the housing in the width of the desired central housing zone an annular groove is inserted. When the housing is rotating, a non-magnetisable filling material is filled into the annular groove while heating the annular groove area, and the rotation of the housing is maintained until solidification of the filling material. Subsequently, the housing is over-turned outside to the final dimension of the outer diameter, so that there is no longer any connection between the magnetizable housing parts. A valve housing produced in this way can be used, for example, in magnetic valves for anti-lock braking systems (ABS) of motor vehicles.

Are known further from the DE 42 37 405 C2 Method for producing a solid core for injection valves for internal combustion engines ( FIG. 5 of the document). The methods are characterized by providing, directly or through previous conversion processes, a one-piece sleeve-shaped magnetic martensitic workpiece which undergoes a local heat treatment in a central portion of the magnetic martensitic workpiece to convert that middle portion into a non-magnetic, austenitic center portion , Alternatively, in the local heat treatment by laser, molten austenite-forming elements are added to the site of the heat treatment to form a nonmagnetic austenitic central portion of the solid core.

From the EP 0 629 711 A1 For example, a method for producing a fixed magnetic circuit component for an electromagnetically operable valve is already known, wherein the magnetic circuit component has at least two zones and in each case two immediately following zones have different magnetic properties. A cup-shaped base of a magnetic or magnetizable material is provided. A complete first heat treatment of the body is made, followed by a local second heat treatment of the body to form a portion with a structure of martensite and retained austenite in the otherwise martensitic body. The base body thus treated is finally installed as a magnetic circuit component in a magnetic circuit of an electromagnetically actuated valve. In the area of a working air gap, a magnetic separation point is present within the otherwise martensitic cup-shaped basic body over the entire thickness of the thin-walled base body around which the magnetic field lines of the magnetic circuit are led in order to attract a magnetic armature against a fixed inner pole when a magnetic coil is energized. The cup-shaped base body is a stationary valve component part of the fixed outer magnetic circuit.

Advantages of the invention

The inventive method for producing a fixed magnetic circuit component with the characterizing features of the main claim has the advantage that in a very simple and cost-effective manner housing with a magnetic separation or magnetic circuit components with locally adjusted magnetic properties, especially in edge layers mass produced reliably.

In particular, due to the simplicity of the individual components only a reduced complexity of special tools compared with the known production methods is necessary.

It is also advantageous that a high flexibility in the design of the geometry of the magnetic circuit component itself, such as. in length, outside diameter, gradations is possible.

It is of particular advantage that coating processes, such as carbonitriding, which are usually necessary for producing edge layers which have been changed in their magnetic properties, can be dispensed with.

The measures listed in the dependent claims advantageous refinements and improvements of the main claim method are possible.

drawing

Embodiments of the invention are shown in simplified form in the drawing and explained in more detail in the following description. Show it FIG. 1 a fuel injection valve according to the prior art with a three-piece inner metal valve tube as a housing, FIGS. 2 to 7 FIG. 2 schematically shows method steps of a known method for producing a fixed magnetic circuit component in the form of a tubular housing, FIG. FIG. 8 a schematic section of an injection valve with such a case, FIGS. 9 to 13 schematically process steps of the method according to the invention for the production of a fixed magnetic circuit component in the form of an anchor bolt, FIG. 14 a schematic section of a magnetic circuit in Tauchankerausführung with an anchor bolt made according to the invention and FIG. 15 a schematic section of a magnetic circuit in Flachankerausführung with an anchor plate produced according to the invention.

Description of the embodiments

Before using the FIGS. 2 to 15 the method steps of the method for producing a fixed magnetic circuit component will be described with reference to FIG. 1 a fuel injection valve of the prior art as a possible input product for a magnetic circuit component produced according to the invention will be explained in more detail.

That in the FIG. 1 For example, shown electromagnetically operable valve in the form of an injector for fuel injection systems of mixture-compressing spark-ignition internal combustion engines has a surrounded by a magnetic coil 1, serving as a fuel inlet nozzle and inner pole tubular core 2, for example, has over its entire length a constant outer diameter. A coil body 3 stepped in the radial direction accommodates a winding of the magnet coil 1 and, in conjunction with the core 2, enables a compact construction of the injection valve in the region of the magnet coil 1.

With a lower core end 9 of the core 2 is concentric with a valve longitudinal axis 10 tightly connected to a tubular metal non-magnetic intermediate part 12 by welding and surrounds the core end 9 partially axially. Downstream of the bobbin 3 and the intermediate part 12 extends a tubular valve seat support 16 which is fixedly connected to the intermediate part 12. In the valve seat carrier 16, an axially movable valve needle 18 is arranged. At the downstream end 23 of the valve needle 18, a spherical valve closing body 24 is provided, on whose circumference, for example, five flats 25 are provided for flowing past the fuel.

The actuation of the injection valve takes place in a known manner electromagnetically. For axial movement of the valve needle 18 and thus to open against the spring force of a return spring 26 and to close the injector, the electromagnetic circuit is used with the solenoid 1, the core 2 and an armature 27. The tubular armature 27 is facing away with a valve closing body 24 End of the valve needle 18 firmly connected by, for example, a weld and aligned with the core 2. In the downstream, the core 2 opposite end of the valve seat carrier 16 is a cylindrical valve seat body 29 having a fixed valve seat 30, mounted by welding tight.

The spherical valve closing body 24 of the valve needle 18 cooperates with the valve seat 30 of the valve seat body 29, which tapers frustoconically in the flow direction. At its lower end face of the valve seat body 29 with an example cup-shaped spray orifice plate 34 is solid and tight by a z. B. connected by means of a laser weld. In the spray perforated disk 34 at least one, for example, four ejection openings 39 formed by eroding or punching are provided.

In order to guide the magnetic flux for optimum actuation of the armature 27 when energizing the solenoid coil 1 and thus for safe and accurate opening and closing of the valve to the armature 27, the magnetic coil 1 of at least one, for example, designed as a bracket and serving as a ferromagnetic element guide element Surrounded surrounding the solenoid coil 1 in the circumferential direction at least partially and with its one end to the core 2 and its other end rests against the valve seat carrier 16 and with these z. B. is connected by welding, soldering or gluing. One inner metal valve tube as a skeleton and thus also the housing of the fuel injection valve form the core 2, the non-magnetic intermediate part 12 and the valve seat carrier 16, which are fixedly connected to each other and extend over the entire length of the fuel injection valve. All other functional groups of the valve are arranged inside or around the valve tube. In this arrangement, the valve tube is the classic three-part structure of a housing for an electromagnetically actuated unit, such as a valve, with two ferromagnetic or magnetizable housing portions, which is effective for effective guidance of the magnetic circuit lines in the region of the armature 27 by means of a non-magnetic intermediate part 12 separated from each other or at least connected to each other via a magnetic throttle.

The injection valve is largely surrounded by a plastic extrusion coating 51, which extends from the core 2 in the axial direction via the magnetic coil 1 and the at least one guide element 45 to the valve seat carrier 16, wherein the at least one guide element 45 is completely covered axially and in the circumferential direction. For example, a mitangespritzter electrical connector 52 belongs to this plastic extrusion 51.

With the in the FIGS. 2 to 7 schematically indicated process steps of not covered by the scope of the method for producing a fixed magnetic circuit component, it is possible in an advantageous manner, particularly simple and inexpensive thin-walled housing 66 for a variety of purposes, including preferably produce electromagnetically operable valves that can replace a three-piece valve tube described above.

In a first process step ( FIG. 2 ), an example cylindrical base body 55 is provided from which the housing 66 is to be made and which consists of a magnetic or magnetizable material and is eg ferromagnetic or ferritic or has a martensitic material structure. The main body 55 may initially be solid and, for example, be obtained for a particularly effective production of many cases 66 of long bar material. The material of the main body 55 is in any case a steel which forms residual austenite and martensite due to its alloy composition. Alloy elements in the material are the austenite-stabilizing elements C, N, Ni and Mn.

In order to achieve the desired different magnetic properties of the magnetic circuit component, the base body 55 is completely subjected to a heat treatment, which can be carried out in ovens 56 by hardening, freezing in freezers and / or by tempering once or several times ( FIG. 3 ). After hardening, the microstructure can also consist of retained austenite parts, which are converted into martensite by the subsequent heat treatment steps. Alternatively, the microstructure may also consist of ferrite with embedded particles such as carbides, nitrides or intermetallic compounds. The heat treatment takes place in such a way that a completely magnetic martensitic material structure is formed in the main body 55 ( FIG. 4 ).

Subsequently, a further heat treatment is performed, which, however, is carried out only locally limited. For this purpose, a partial area of the main body 55 is exposed to a short-time heat treatment by means of laser or induction heating 57 (FIG. FIG. 5 ). In this way, the material of the base body 55 is locally austenitized and homogenized in the portion of the second heat treatment and consists after cooling of the body 55 or the self-quenching by the surrounding material of martensitic areas 58 and the subarea 59 with martensite and retained austenite ( FIG. 6 ). The main body 55 now consists of zones with different structures and magnetic properties.

The base body 55 is subsequently finished so that a solid housing 66 is present as a magnetic circuit component in a desired geometry. In the case of using a housing 66 produced according to the invention in a fuel injection valve, it may be advantageous to mold the housing 66 specifically by manufacturing measures such as stretching, rolling, swaging, crimping and / or Auftulpen. With the housing 66 is a component which, in a known fuel injection valve according to FIG. 1 the sum of the functions of the valve tube consisting of the core 2, intermediate part 12 and valve seat carrier 16 can completely take over and thus extends, for example, over the entire axial length of a fuel injection valve.

The massive body 55 is brought by manufacturing measures, for example in a tubular sleeve shape. The massive body 55 can either before or only after the local heat treatment with an inner longitudinal opening 60 to form the tubular housing 66 are provided ( FIG. 7 ).

FIG. 8 shows a schematic section of a fuel injector with a housing 66 produced according to the invention, which is installed as a thin-walled sleeve in the valve and thereby surrounds the core 2 and the armature 27 radially and circumferentially and is itself surrounded by the magnetic coil 1. It is clear that the changed in its magnetic properties and martensitic and rest austenitic portion 59 of the housing 66 in the axial extension of a working air gap 70 between the core 2 and the armature 27 is to guide the magnetic circuit lines optimally and effectively in the magnetic circuit. Instead of in FIG. 1 shown bow-shaped guide member 45, the outer magnetic circuit component is designed for example as a magnetic pot 46, wherein the magnetic circuit between the magnetic pot 46 and the housing 66 is closed by a cover member 47. The inventive method also makes it possible to locally change housing 66 with larger wall thicknesses in their magnetic properties, so that a higher internal pressure resistance while still minimizing the magnetically active area is ensured in favor of the magnetic force.

FIGS. 9 to 13 schematically show process steps of the inventive method for producing a fixed magnetic circuit component in the form of an anchor bolt 66 '. The manufacture of the anchor bolt 66 'takes place in a manner comparable to the previously described production of the housing 66 according to FIG FIG. 7 , In a first process step ( FIG. 9 ), for example, a thin cylindrical base body 55 'is provided, from which the anchor bolt 66' is to be manufactured and which consists of a magnetic or magnetizable material and is eg ferromagnetic or ferritic or has a martensitic material structure. The main body 55 'can be obtained, for example, for a particularly effective production of many anchor bolts 66' of long bar material. The material of the main body 55 'is in any case a steel which forms retained austenite and martensite due to its alloy composition. Alloy elements in the material are the austenite-stabilizing elements C, N, Ni and Mn.

To achieve the desired different magnetic properties of the magnetic circuit component of the main body 55 'is completely a heat treatment which can be carried out, for example, by means of hardening, freezing in freezers or by firing once or several times in ovens 56 ( FIG. 10 ). After hardening, the microstructure can also consist of retained austenite parts, which are converted into martensite by the subsequent heat treatment steps. Alternatively, the microstructure may also consist of ferrite with embedded particles such as carbides, nitrides or intermetallic compounds. The heat treatment takes place in such a way that a completely magnetic martensitic material structure is formed in the main body 55 '( FIG. 11 ).

Subsequently, a further heat treatment is performed, which is to lead exclusively to the surface in the edge regions of the base body 55 'to a change in the magnetic properties. The surface of the main body 55 'is subjected to a short-time heat treatment by means of laser or induction heating 57 ( FIG. 12 ). In this way, the material of the base body 55 'is austenitized locally on the surface and homogenized and consists after cooling of the body 55' and the self-quenching by the surrounding material of an inner martensitic region 58 'and an outer edge region 59' with martensite and Retained austenite ( FIG. 13 ). The main body 55 'or the anchor bolt 66' now consists of zones with different structures and magnetic properties.

If necessary, the base body 55 'is subsequently finished so that a fixed anchor bolt 66' is present as a magnetic circuit component in a desired geometry. FIG. 14 shows a schematic section of a magnetic circuit in Tauchankerausführung with an anchor bolt 66 'produced according to the invention, which dives through a magnet coil 1 enveloping magnetic pot 46 and is movable there. In the case of solenoid plunger circuits, the dynamics and the magnetic force of the solenoid valve can be improved with an anchor bolt 66 'in which the outer edge region 59' has retained austenite components. Coating processes, such as carbonitriding, can be dispensed with.

In FIG. 15 2 shows a schematic section of a magnetic circuit in flat armature design with an armature plate 66 "produced according to the invention. comparable. The local second heat treatment is carried out in such a way that on one side of the flat plate-shaped base body, a short-time heat treatment is carried out by means of laser or induction heating. In this way, the material of the body is locally austenitized and homogenized on this side and consists after cooling of the body or the self-quenching by the surrounding material of a martensitic region 58 "and the magnetic coil 1 facing edge region 59" with martensite and retained austenite. The anchor plate 66 "now consists of zones with different structures and magnetic properties.

This additional air gap in the edge region 59 "can be used to prevent the anchor plate 66" from sticking to the magnetic pot 46 in order to set a defined residual air gap in the magnetic circuit or as an air gap To serve wear protection.

The invention is by no means limited to use in fuel injection valves or solenoid valves for anti-lock braking systems, but relates to all electromagnetically actuated valves of different application areas and generally all solid housing in units in which zones of different magnetism are sequentially required.

Claims (6)

1. Method for producing a rigid magnetic circuit component (66, 66', 66'') for an electromagnetically operable valve,
   the magnetic circuit component (66, 66', 66'') having at least two zones and every two directly successive zones having different magnetic properties, comprising the method steps of:

   a) providing a main body (55, 55') of a magnetic or magnetizable material;

   b) a complete first heat treatment of the main body (55, 55');

   c) a local second heat treatment of the main body (55, 55') to form a subregion (59) or a surface region (59', 59") having a microstructure of martensite and residual austenite in an otherwise martensitic main body (55, 55'), and

   d) installing the finished main body (55, 55') as a magnetic circuit component (66', 66'') in a magnetic circuit,

   characterized in that
   the main body (55, 55') is provided as a solid bolt or as a flat plate,
   the local second heat treatment of the main body (55, 55') is performed in such a way that the main body (55, 55') is locally austenized and homogenized at the surface,
   so that, in the case of the solid bolt, after the cooling or a self-quenching by the surrounding material, the main body (55, 55') consists of an inner martensitic region (58') and an outer surface region (59') with martensite and residual austenite, or
   so that, in the case of the flat plate, after the cooling or a self-quenching by the surrounding material, the main body (55, 55') consists of a martensitic region (58") and a surface region (59"), to be installed facing a magnetic coil (1), with martensite and residual austenite,
   and
   is then installed as a solid anchor bolt (66') or as a flat anchor plate (66") in a magnetic circuit.
2. Method according to Claim 1, characterized in that the main body (55, 55') is ferromagnetic or has a ferritic or martensitic material structure.
3. Method according to either of the preceding claims, characterized in that the first heat treatment of the main body (55, 55') takes place by means of hardening, deep cooling in freezing cabinets, or tempering one or more times in furnaces (56).
4. Method according to one of the preceding claims, characterized in that the local second heat treatment of the main body (55, 55') takes place by means of laser or induction heating (57).
5. Method according to one of the preceding claims, characterized in that, after the local second heat treatment of the main body (55, 55'), a final working of the main body (55, 55') obtained in this way is performed until a desired geometry of the magnetic circuit component (66', 66'') is achieved.
6. Method according to Claim 5, characterized in that the final working of the main body (55, 55') takes place by means of quenching, tumbling, swaging, flanging and/or flaring.

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