DE102011077179A1 - Anchor for a solenoid valve and method of making an armature - Google Patents

Abstract

An armature (3), which is used for a solenoid valve (2), comprises an armature shaft (4) and an armature plate (5). In particular, the solenoid valve (2) can be used here for a fuel injection valve of an air-compressing, self-igniting internal combustion engine. The anchor plate (5) is made of a magnetic material. Furthermore, the anchor plate (5) and the anchor shank (4) are cohesively connected to one another by sintering. In addition, a method for producing such an anchor (3) is given.

Description

State of the art

The invention relates to an armature for a solenoid valve, which is used in particular for fuel injection valves of air-compressing, self-igniting internal combustion engines, and a method for producing such an armature.

From the DE 10 2006 021 741 A1 For example, a fuel injector with a pressure compensated control valve is known. The injector serves to inject fuel into a combustion chamber of an internal combustion engine. In this case, an injection valve member is provided which releases or closes at least one injection opening. The injection valve member is driven by a control valve, wherein the control valve releases or closes a connection from a control chamber into a fuel return. The control valve is controlled by a magnetic circuit. As soon as the magnetic coil is energized, a magnetic field is formed which acts on an armature. In the anchor in this case a bore is formed, in which a valve needle is guided. In addition, the armature is followed by a sleeve, which serves as a guide for the valve needle. In addition, the armature is accommodated in an armature space, in which the fuel flows out of a control chamber when the control valve is open. From the armature space, the fuel enters the return line. To start an injection process, the solenoid is energized. The magnetic field then pulls the armature in the direction of the magnetic core. As a result, the valve needle is moved together with the armature in the direction of the magnetic core. From the control chamber can then flow under system pressure fuel via an outlet throttle in the armature space and thus to the return. This causes the pressure in the control room to decrease. As a result, with respect to a balance of forces on the control piston, which controls an injection valve member, an opening force is exerted and the control piston moves into the control chamber. This results in a movement of the injection valve member in the direction of the control piston, whereby at least one injection port is released and fuel flows into the combustion chamber of the internal combustion engine.

The from the DE 10 2006 021 741 A1 known fuel injector has the disadvantage that especially at high pressures to be switched high dynamic forces, especially during rapid closing, occur, which act on the anchor. Thus, a robust design is required to ensure this reliable lifetime switching. The material used for the design of the armature must therefore meet both the high mechanical and magnetic requirements. This makes the design of the anchor on the one hand expensive and limited to the other still the possible application.

Disclosure of the invention

The armature according to the invention with the features of claim 1, the fuel injection valve according to the invention with the features of claim 6 and the inventive method with the features of claim 7 have the advantage that an improved design is possible, in particular an economical production for a wide range of applications possible is.

The measures listed in the dependent claims advantageous refinements of the anchor specified in claim 1, the fuel injection valve specified in claim 6 and the method specified in claim 7 are possible.

It is advantageous that the cohesive connection between the armature plate and the armature shaft is formed at least substantially over the entire joining surface between the armature plate and the armature shaft. In general, connection methods are conceivable in which substantially point- or line-shaped substance connections are configured. This is possible, for example, in welding or soldering processes. By the sintered connection, however, a cohesive connection can be realized on the entire joint surface, without thereby increasing the production cost.

As a result, a high strength of the connection can be achieved, wherein the process implementation is economical. Furthermore, depending on the configuration, a pressure compensated switching valve can be realized. However, non-pressure compensated servo valves can be realized. Also valves for injectors or other applications can be realized. Furthermore, magnetic actuators can be created, which serve as a direct switch without servo function.

It is also advantageous that the magnetic material of the anchor plate made of iron and / or silicon and / or phosphorus is formed. Here, the magnetic material may also have a high silicon content. Although such a magnetic material is comparatively brittle, connecting the anchor plate to the anchor shaft is still possible via sintering. This also results in a significant advantage with respect to other connection methods, in particular a mechanical joining method. Accordingly, it is possible that the magnetic material of the armature plate is advantageously formed of iron and cobalt. Such an alloy of iron and cobalt can in this case without additional alloying elements be predetermined. The joining of this also comparatively brittle material can also be realized by sintering.

It is also advantageous that the armature shaft is formed of a material having a high carbide content. Also possible are ceramics, hard metals and cermets as materials for the armature shaft and phosphorus-containing metals as materials for the armature. By sintering namely joining of such materials is possible, which is problematic welding, for example. In this case, other materials that show poor weldability can be used. Specially phosphorus-containing materials, ceramics, in particular ZrO2, hard metals and cermets. In addition, wear-resistant steels, in particular tool steels or high-carbide high-speed steels, can also be used.

This results in significant advantages in the proposed connection method by sintering. In contrast to welding or soldering, no badly connected areas or stress cracks occur in the joining zone, so that process reliability increases. In addition, residual stresses in the armature plate can be reduced over conventional designs, resulting in improved magnetic properties.

Due to the high strength of the compound designed by sintering, it is also possible that the joining zone is made smaller than in conventional joining methods, so that more geometric freedom in the component design is made possible.

In carrying out the method, it is also advantageous that in the green part of a bore, in particular a through hole or blind hole, is configured and that an inner diameter of the bore of the green part is set greater than an outer diameter of the arranged in the bore anchor shaft in the region of the bore. Since the green part shrinks during sintering, by specifying a certain amount of play, it is possible to generate a preferably small oversize, which still degrades during sintering due to a plastic deformation of the anchor plate. After the formation of a contact between the material of the armature shaft and the material of the plate sets a diffusion exchange between the two materials, whereby a cohesive connection is formed. As a result, a high shear strength of the joining zone is achieved. Another advantage is that the sintering and joining can take place in one process step. This reduces the process costs.

It is also advantageous that in addition to a joining surface between the armature shaft and the armature plate in at least one direction along an axis of the armature shaft, a positive connection is formed. As a result, the shear strength at the joining zone or joining surface can be further improved. Specifically, the mechanical strength of the shear strength can be further increased.

It is also advantageous here that the armature shaft has at least one projection on the joining surface between the armature shaft and the armature plate. Such a projection may, for example, be pin-shaped and extend radially to the axis of the armature shaft. Especially in this case, it is advantageous that the green part is composed of at least two partial plates, in particular two half-plates, which are positioned on both sides on the projection of the armature shaft. As a result, the partial plates can be pre-pressed and then positioned on the armature shaft. This simplifies the manufacture of the anchor. In addition, this can be given a certain clearance between the green part of the sub-plates and the armature shaft, which leads to a desired excess due to the sintering shrinkage.

Brief description of the drawings

Preferred embodiments of the invention are explained in more detail in the following description with reference to the accompanying drawings, in which corresponding elements are provided with identical reference numerals. It shows:

1 a fuel injection valve in an excerpt, schematic sectional view according to an embodiment of the invention;

2 a partial, schematic representation of an anchor for in 1 illustrated fuel injection valve according to a first possible embodiment of the invention;

3 the in 2 illustrated anchor according to a second possible embodiment of the invention;

4 the in 2 illustrated anchor according to a third possible embodiment of the invention;

5 the in 2 illustrated anchor according to a fourth possible embodiment of the invention;

6 the in 2 illustrated anchor according to a fifth possible embodiment of the invention;

7 the in 2 illustrated anchor according to a sixth possible embodiment of the invention and

8th the in 2 illustrated anchor according to a seventh possible embodiment of the invention.

Embodiments of the invention

1 shows an embodiment of a fuel injection valve 1 of the invention in an excerpt, schematic sectional view. The fuel injector 1 is particularly suitable for fuel injection systems of air-compressing, self-igniting internal combustion engines. Specifically, the fuel injector is suitable 1 for a direct injection in which diesel or similar fuels are injected under high pressure into the combustion chamber of an internal combustion engine. The fuel, which serves as a hydraulic medium, for example, with a pressure of up to 250 MPa (2500 bar) are injected into the combustion chamber. The fuel injector 1 However, it is also suitable for other applications.

The fuel injector 1 has a solenoid valve 2 with an anchor 3 on. The anchor 3 includes an anchor shaft 4 and an anchor plate 5 , In addition, the solenoid valve 2 a magnet pot 6 on, which is a magnetic coil 7 receives.

The fuel injector 1 also has a nozzle needle 8th on that in a fuel room 9 is arranged. The nozzle needle 8th includes a valve closing body 10 that with a valve seat 11 cooperates to a sealing seat. When the nozzle needle 8th from their seat on the valve seat surface 11 lifts, then fuel can from the fuel space 9 via one or more nozzle bores 12 be injected into the combustion chamber of an internal combustion engine.

The actuation of the nozzle needle 8th does not take place directly from the solenoid valve 2 but indirectly via a hydraulic control, as indicated by the double arrow 13 is illustrated. This is when pressing the solenoid valve 2 in a known manner, a fuel flow through an outlet throttle 14 released and when closing the solenoid valve 2 locked again, so that in a known manner, a control of the nozzle needle 8th results.

For example, the nozzle needle 8th be surrounded in the open state of substantially the same pressure, so that there is a force-balanced situation, while in the closed state, a closing force on the nozzle needle 8th resulting from the hydraulic pressure and the cross section of the sealing seat of the nozzle needle 8th determined and which may typically be in the range of a few hundred Newton.

The switching of the solenoid valve 2 takes place via the magnet pot 6 and the magnetic coil 7 , indicating the reduction of a working air gap 15 between the magnet pot 6 and the anchor plate 5 of the anchor 3 based. This is done in response to the over this working air gap 15 excited magnetic field. The magnetic force generated in this way is particularly large when the working air gap 15 is small. Starting from a normally open state increases in particular the force in the course of the working path. Since the hydraulic force balance begins only in the course of the movement, the power requirement in the first moment of opening is maximum. That is, the largest power requirement occurs at the time in which the magnetic force is inherently minimal.

The power required to open the nozzle needle 8th However, it is reduced because the nozzle needle 8th not directly to the magnetic actuator 6 ' from the magnet pot 6 and the magnetic coil 7 is coupled. Instead, via the magnetic actuator 6 ' opening the outlet throttle 14 achieved so that one with the nozzle needle 8th hydraulically coupled volume, which initially is at high pressure, is relaxed, while at the same time a second with the nozzle needle 8th hydraulically coupled volume remains at high pressure. In this way, the nozzle needle 8th opened by hydraulic forces, which significantly reduces the power requirement.

The solenoid valve 2 preferably has a shallow anchor 3 with an at least largely flat anchor surface 16 on. The flat anchor 3 is thus as a flat anchor 3 designed. The magnet pot 6 has an inner pole. The anchor 3 closes over the working air gap 15 in the actuated state, the magnetic circuit. As a result, the actuation of the solenoid valve takes place 2 , An embodiment as a plunger anchor is possible.

The anchor shaft 4 of the anchor 3 fulfills several functions. First, over the length of the anchor shaft 4 the anchor 3 led and secondly closes a lower section 17 of the anchor shaft 4 the solenoid valve 2 , The requirements for the wear and impact resistance of the anchor shaft 4 are therefore very high. About the anchor plate 5 of the solenoid valve 2 becomes the magnetic circuit of the magnetic actuator 6 ' closed. The requirements for the magnetic properties of the material of the anchor plate 5 are therefore particularly high. this concerns in particular a saturation polarization and a resistivity of the anchor plate 5 ,

The concept of anchor plate 5 is to be understood generally. The anchor plate 5 can be performed, for example, in different geometries depending on the magnetic and hydraulic requirements or boundary conditions. Here, for example, a full-surface or slotted configuration are conceivable. Also an embodiment with holes in the anchor plate 5 is possible, for example.

Advantageously, the anchor 3 made of two different materials. Here is the anchor shaft 4 made of a material selected in relation to the desired strength. The magnetic material of the anchor plate 5 is, on the other hand, selected with respect to the magnetic requirements. However, this results in the problem that a reliable connection between the armature shaft 4 and the anchor plate 5 must be guaranteed.

In the case of a conventional anchor made of only one material, the mechanical requirements with respect to the anchor shaft as well as the magnetic requirements with respect to the anchor plate must be met at the same time. However, this requires a compromise and possibly requires high material costs.

The design of at least two materials can be a mechanically outstanding material for the armature shaft 4 and a magnetically outstanding material for the anchor plate 5 be used.

In principle, it is conceivable that the anchor 3 is assembled by a mechanical joining method of two parts, namely an anchor shaft and an anchor plate. However, such a connection, for example by peeling rivets, leads to new problems. Because by the joining process, a significant mechanical deformation can occur. Specifically, mechanical stresses in the anchor plate 5 occur, which are unfavorable to the magnetic properties and, where appropriate, to the desired planar geometry of the anchor surface 16 impact. In addition, the possible material combinations are limited here. In particular, no brittle materials can be used.

The production of the anchor 3 Therefore, by connecting the anchor plate 5 with the anchor shaft 4 by sintering. This is a cohesive connection between the anchor plate 5 and the armature shaft 4 reached. This results in a joint surface 18 between the anchor shaft 4 and the anchor plate 5 , which is designed by sintering in a characteristic way. The term joining surface 18 is here to be understood in general and also includes a zonal configuration (joining zone) or a regional design (joining region) of the sintered connection. Because during the sintering process, there is the diffusion exchange between the two materials.

Possible embodiments of the connection between the anchor plate 5 and the armature shaft 4 of the anchor 3 are below with reference to the 2 to 8th described in more detail.

2 shows a partial, schematic representation of an anchor 3 for a solenoid valve 2 a fuel injection valve 1 according to a first possible embodiment of the invention. The anchor shaft 4 is designed cylindrical for simplicity. Here is the anchor shaft 4 as a massive anchorage 4 shown without holes. Depending on the application, the anchor shaft 4 also have other geometries and holes. Specifically, axial bores may be provided extending along an axis 20 of the anchor shaft 4 of the anchor 3 through the anchor shaft 4 extend.

For the production of the two-part anchor 3 About the Sinterfügeverfahren come the already sintered or melt metallurgically produced anchor shaft 4 and a powder metallurgically produced, in particular pressed, green part 5 ' for the anchor plate 5 for use. Both parts 4 . 5 ' In this case, they may already have a contour suitable for fulfilling the function, as a result of which reworking can be minimized or even completely eliminated, depending on the required tolerances. The green part 5 ' for the anchor plate 5 has in this embodiment as a through hole 21 configured bore 21 on. Through this hole 21 becomes the anchor shaft 4 passed through, wherein the armature shaft 4 and the green part 5 ' be positioned relative to each other. The anchor shaft 4 This is preferably in the bore with little play 21 inserted. An inner diameter 22 the bore 21 is set slightly larger than an outer diameter 23 of the anchor shaft 4 in the area of the bore 21 , During the subsequent sintering, the green part shrinks 5 ' for the anchor plate 5 on the anchor shaft 4 on. The sintering shrinkage and the initial play between the armature shaft 4 and the green part 5 ' are here by specifying the inner diameter 22 and the outside diameter 23 coordinated so that a small excess is generated during sintering. This builds up during the sintering by a plastic deformation of the material for the anchor plate 5 from. After the formation of the contact between the material of the armature shaft 4 and the material of the anchor plate 5 uses a diffusion exchange between both materials, whereby a cohesive connection to the joint surface 18 is trained. This results in a high shear strength of the joining zone 18 achieved. After sintering, the two-piece anchor 3 be mechanically reworked depending on the required tolerances if necessary. If necessary, hardening and tempering is possible. Thus, a tempering can be done.

For the anchor shaft 4 Above all, materials are suitable which have a high resistance to wear and whose properties are not significantly changed by the sintering process. It is advantageous if the material for the anchor shaft 4 subsequently no longer has to be hardened, as this leads to a deterioration of the soft magnetic properties of the material of the anchor plate 5 can lead. Ceramic materials, in particular ZrO 2, hard metals and so-called cermets fulfill these criteria and are therefore examples of suitable materials for the anchor shaft 4 , But it is also possible, wear-resistant steels, especially tool steels or high-speed steels, as a material for the anchor shaft 4 which can be locally cured or through-hardened after the sinter-joining process.

For the material of the green part 5 ' or for the anchor plate 5 For example, materials with good soft magnetic properties can be used. For example, the magnetic material for the anchor plate 5 based on an alloy of iron and silicon, an alloy of iron, silicon and phosphorus, an alloy of iron and chromium or an alloy of iron and cobalt or an alloy of iron and phosphorus.

When using the 2 described embodiment is the bore 21 cylindrically shaped. Here is also the anchor shaft 4 cylindrically shaped.

3 shows the in 2 illustrated anchor 3 according to a second possible embodiment of the invention. In this embodiment, the armature shaft 4 a rejuvenation 25 on, passing through a circumferential annular groove 25 is formed. The outer diameter 23 of the armature shaft 4 in the area of the bore 21 This is smaller than an outer diameter 26 of the anchor shaft 4 in the remaining area. The inner diameter 22 the bore 21 can be slightly larger than the outer diameter 26 be elected. This allows a joining together. In the subsequent sintering results in addition to the cohesive connection and a positive connection. The rejuvenation 25 This is preferably as a small rejuvenation 25 educated.

4 shows the in 2 illustrated anchor 3 according to a third possible embodiment of the invention. In this embodiment, the shear strength of the joint zone 18 by a mechanical toothing 27 even further increased. The mechanical gearing 27 can be configured for example by a thread. It is possible that the green part 5 ' before sintering onto a threaded portion of the armature shaft 4 is screwed on. In this case it is also possible that the inner diameter 22 of the green part 5 ' is greater than the outer diameter 23 of the anchor shaft 4 , Depending on the configuration, the mechanical toothing 27 However, before sintering also be executed without a game.

5 shows the in 2 illustrated anchor 3 according to a fourth possible embodiment of the invention. In this embodiment, the armature shaft 4 a conical section 28 on. In addition, the hole 21 also tapered and in shape to the conical section 28 of the anchor shaft 4 customized. Through the conical joining zone 18 This results in a mechanical support of the anchor plate 5 relative to the armature shaft 4 in one direction 29 along the axis 20 , This can on the one hand facilitate the joining and thus the implementation of the sintering process. On the other hand, this can ensure an additional positive connection.

6 shows the in 2 illustrated anchor 3 according to a fifth possible embodiment of the invention. In this embodiment, the bore 21 as a blind hole-shaped bore 21 designed. An end section 30 of the anchor shaft 4 is in the hole before sintering 21 inserted. This can be a certain game by choosing the inner diameter 22 and the outside diameter 23 be specified. In this embodiment, there is the advantage that the armature shaft 4 for sintering in the hole 21 of the green part 5 ' can be made. In addition, in addition to the cohesive connection also results in a positive connection or support in the direction 29 ,

This embodiment is particularly suitable for a plunger-armature geometry.

7 shows the in 2 illustrated anchor 3 according to a sixth possible embodiment of the invention. In this embodiment, the armature shaft 4 one or more projections 31 on. For example, the projection 31 as a ridge-shaped projection 31 be designed, with respect to the axis 20 preferably in radial Direction extends. The lead 31 can be designed in particular as a pin-shaped projection. The lead 31 However, it can also be done by a circulating collar 31 be formed. Furthermore, other embodiments are conceivable.

For the production of the green part 5 ' it is possible that the starting material, in particular a powder for the starting material, in the region of the projection 31 around the anchor shaft 4 is pressed around. Subsequently, the sintering takes place.

8th shows the in 2 illustrated anchor 3 according to a seventh possible embodiment of the invention. In this embodiment, the green part 5 ' from several partial plates 32 . 33 composed. Preferably, two half plates 32 . 33 provided to the green part 5 ' to build. There is the advantage that the half plates 32 . 33 as pre-pressed green bodies first on the anchor shaft 4 can be positioned. This can be done from both ends of the armature shaft 4 in each case one of the partial plates 32 . 33 on the anchor shaft 4 be joined, so the lead 31 or the plurality of projections 31 on both sides the projection 31 lock in. Subsequently, the sintering takes place around the green part 5 ' for the anchor plate 5 with the anchor shaft 4 connect to. Preferably, the half plates 32 . 33 Equally designed.

Another advantage is that the half plates 32 . 33 without additional effort with an inner diameter 22 the bore 21 can be configured which is larger than the outer diameter 23 of the anchor shaft 4 in the area of the projection 31 , As a result, a specific game can be specified, which is during sintering due to the shrinkage of the green part 5 ' to specify a desired oversize.

Among the possible embodiments described, inter alia, within certain limits are any cross-sectional geometries of the joining zones 18 predetermined.

Thus, the integral connection without an intermediate layer, such as a soldering material, an adhesive or a weld, between the armature shaft 4 and the anchor plate 5 be configured, yet a cohesive connection is realized. This plastic deformation, as they occur for example in a peel, can be avoided.

The invention is not limited to the described embodiments.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• DE 102006021741 A1 [0002, 0003]

Claims (11)

Anchor ( 3 ) for a solenoid valve ( 2 ), which is used in particular for fuel injection valves of air-compressing, self-igniting internal combustion engines, with an armature shaft ( 4 ) and an anchor plate ( 5 ), characterized in that the anchor plate ( 5 ) is formed of a magnetic material and that the anchor plate ( 5 ) and the armature shaft ( 4 ) are interconnected by sintering cohesively. Anchor according to claim ( 1 ), characterized in that the cohesive connection between the anchor plate ( 5 ) and the armature shaft ( 4 ) at least substantially over the entire joint surface ( 18 ) between the anchor plate ( 5 ) and the armature shaft ( 4 ) is trained. Anchor according to claim 1 or 2, characterized in that the magnetic material of the anchor plate ( 5 ) is formed at least substantially of iron silicon and / or iron phosphorus and / or iron silicon phosphorus. Anchor according to claim 1 or 2, characterized in that the magnetic material of the anchor plate ( 5 ) is formed of iron and cobalt or of iron and chromium. Anchor according to one of claims 1 to 4, characterized in that the armature shaft ( 4 ) is formed of a ceramic, a cemented carbide, a cermet or a wear-resistant steel, in particular a tool steel or a high-speed steel. Fuel Injector ( 1 ), in particular injector for air-compressing, self-igniting internal combustion engines, with a solenoid valve ( 2 ), which has an anchor ( 3 ) according to one of claims 1 to 5. Method for producing an armature suitable for a solenoid valve ( 2 ), with an anchor shaft ( 4 ) and an anchor plate ( 5 ), the method comprising the following steps: - powder metallurgy production of a green part ( 5 ' ) for the anchor plate ( 5 ) of a magnetic material and - sintering of the armature shaft ( 4 ) and of the armature shaft ( 4 ) arranged green part ( 5 ' ) for forming the anchor plate ( 5 ) from the green part ( 5 ' ) and the material connection of the anchor plate ( 5 ) with the armature shaft ( 4 ). Method according to claim 7, characterized in that in the green part ( 5 ' ) a hole ( 21 ), in particular a through-bore ( 21 ) or a blind hole ( 21 ), and that an inner diameter ( 22 ) of the bore ( 21 ) of the green part ( 5 ' ) is greater than an outer diameter ( 26 ) of the hole ( 21 ) arranged Aktorschafts ( 4 ) in the area of the bore ( 21 ). Method according to claim 7 or 8, characterized in that at a joining surface ( 18 ) between the armature shaft ( 4 ) and the anchor plate ( 5 ) in at least one direction ( 29 ) along an axis ( 20 ) of the anchor shaft ( 4 ) In addition, a positive connection is formed. Method according to one of claims 7 to 9, characterized in that the armature shaft ( 4 ) at a joint surface ( 18 ) between the armature shaft ( 4 ) and the anchor plate ( 5 ) at least one projection ( 31 ) having. Method according to claim 10, characterized in that the green part ( 5 ' ) from at least two partial plates ( 32 . 33 ) is assembled on both sides of the projection ( 31 ) of the anchor shaft ( 4 ).

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