WO2015110199A1

WO2015110199A1 - Method for producing a magnetic valve

Info

Publication number: WO2015110199A1
Application number: PCT/EP2014/075286
Authority: WO
Inventors: Christian Suenkel; Joerg Abel; Martin Buehner; Guido Pilgram; Thomas Sailer
Original assignee: Robert Bosch Gmbh
Priority date: 2014-01-22
Filing date: 2014-11-21
Publication date: 2015-07-30
Also published as: DE102014201097A1

Abstract

The invention relates to a method for producing a magnetic valve, particularly a fuel injection valve, comprising a valve needle that is guided so as to be displaceable in the axial direction, a magnetic core, and an armature arranged to lie axially opposite said magnetic core, said armature being arranged on the valve needle and having a first base material, the magnetic core having a second base material and, in a high-pressure nitriding process (HT-N process), a first diffusion layer being produced on the first base material and/or a second diffusion layer being produced on the second base material.

Description

Description title

Method of manufacturing a solenoid valve prior art

The invention relates to a method for producing a solenoid valve according to the preamble of claim 1.

Such methods are well known. The hardness of stainless steels is for many applications where wear or a sudden

Stress occurs, typically insufficient.

In electromagnetically actuated magnetic actuators for the actuation of

Solenoid valves, in particular of injection valves, it is known that to increase the wear resistance to impact and rubbing wear the contact partners (armature and inner pole) with a

Chrome layer to be coated

As a rule, such chromium layers are wet-chemically

electrolytic deposition of hexavalent chromium (Cr ⁶⁺ ) produced.

The disadvantage here, however, is that the application of the hard chrome layer is typically comparatively expensive, so that the avoidance of such, in particular galvanically applied, hard chrome layer is desirable. Furthermore, Cr ^{6+ has} a comparatively high toxicity.

Disclosure of the invention

It is an object of the present invention to propose a method for producing a solenoid valve, which without Cr6 + as a process material gets along and is cheaper, yet the magnetic

Properties of the base material remain largely intact.

The inventive method for producing a solenoid valve and the solenoid valve according to the invention according to the independent claims have the advantage over the prior art that, as an alternative to the chromium plating, a thermal process for the production

wear-resistant surfaces of the first and second base material

is provided, wherein in particular the magnetic properties of the base material are largely retained. Toxic Cr ⁶⁺ is no longer used here. In addition, the manufacturing process is much cheaper compared to the chrome plating. In particular, the invention enables the production of a nitrogen-hardened layer with low scattering over various batches of material with different chemical properties

Composition.

Nitrogen is preferably used during the high pressure embroidering process (HT-N process) in a nitrogen atmosphere with 0.5-3.5 bar gauge - i. a nitrogen gas pressure equal to the sum of atmospheric pressure (1013.25 hectopascal) and gauge pressure - at holding temperatures between 1000 ° C and 1300 ° C in the base material - i. the first and second base material - diffused. Holding times and holding temperatures are to be chosen in particular such that the following properties are achieved:

- The first and / or second base material has in the region of the first and / or second diffusion layer hardness between 550 HV (Vickers hardness) and 700 HV, and / or

a layer thickness of the first and / or second diffusion layer is between 100 microns and 250 microns, and / or

- By the HT-N process, the structure of the first and / or second base material is not or only negligibly influenced, and / or

- The magnet armature and / or magnetic core has a relatively high permeability in the first or second base material and in the first or

second diffusion layer - which is also referred to as edge layer - on, - in the HT-N process is a saturation induction relative to the

Base state not reduced (no rest of it). Preferably, the first and / or second base material comprises a microstructure with a material - in particular stainless steels - which are in particular originally ferrite, preferably ideally ferromagnetic, set. By embroidering beyond 1000 ° C. (austenitizing) it is achieved that nitrogen (in particular in sufficient quantities) dissolves in the matrix (of the structure of the first and / or second base material). A fast cooling counteracts good magnetic properties but leads to the targeted

Hardness increase due to martensite formation. Slow cooling would lead to the formation of Cr nitrides, which, although increasing the hardness, use nitrogen to bind the chromium in larger quantities, thus drastically reducing corrosion resistance. According to the HT-N process is performed so that holding times and annealing temperatures (holding temperatures) are reduced with a high nitrogen supply at the same time.

By the method for producing the material properties of the

Magnetic anchor and / or magnetic core (hard diffusion layer with at the same time little influence on the magnetic properties of the base material) is in a particularly advantageous manner, an adjustment of this

Material properties realized with low dispersion over various batches of material with different chemical composition. Preferably, the magnet armature and / or magnetic core (inner pole) on a stainless steel material, which in particular due to a predetermined range of variation of the chemical composition at temperatures beyond 1100 ° C has a comparatively strongly fluctuating austenite content. Accordingly, the possible martensite content and thus the saturation polarization, permeability and coercivity vary after freezing and tempering.

Advantageous embodiments and developments of the invention are the dependent claims, as well as the description with reference to the

Drawings removable.

According to a further preferred development, it is provided that in the HT-N process a holding time and / or a holding temperature are controlled in such a way, a magnetic saturation induction of the first diffusion layer is different from a magnetic saturation induction of the first basic body by less than 20%, preferably less than 10%, more preferably less than 1%, most preferably less than 0.1%, and / or or,

a magnetic saturation induction of the second diffusion layer is different from a magnetic saturation induction of the second basic body by less than 20%, preferably less than 10%, more preferably less than 1%, most preferably less than 0.1%, in particular the structure of the first and / or second base material ferritic, preferably ferromagnetic, particularly preferably ideal

ferromagnetic, is set.

In this way, it is advantageously possible to produce a nitrogen-hardened first and / or second diffusion layer, wherein the magnetic properties of the first and / or second base material nevertheless remain intact. in the

Unlike wear solutions (Cr layer), the adhesion resistance is not adversely affected in the inventive diffusion layer, since the diffusion layer does not grow, but in the core continuously "grows".

According to a further preferred development, it is provided that in the HT-N process the holding time and / or holding temperature is controlled such that the first and / or second base material in the region of the first and / or second diffusion layer has a Vickers hardness between 100 HV and 800 HV, preferably between 400 HV and 750 HV, more preferably between 550 HV and 700 HV.

This makes it possible advantageously, a relatively wear-resistant

Solenoid valve provide.

According to a further preferred development, it is provided that in the HT-N process the holding time and holding temperature are controlled such that the first and / or second diffusion layer has a layer thickness between 10

Micrometers and 500 microns, preferably between 50 microns and 350 microns, more preferably between 100 microns and 250 microns, having.

According to a further preferred embodiment, it is provided that in the HT-N process nitrogen in the first and / or second base material at a nitrogen pressure between 0 bar and 5 bar, preferably between 0, 1 and 4 bar, more preferably between 0.5 bar and 3.5 bar and / or one

Keeping temperature between 800 ° C and 1500 ° C, preferably between 900 ° C and 1400 ° C, more preferably between 1000 ° C and 1300 ° C, is diffused.

As a result, it is advantageously possible to produce a nitrogen-hardened first and / or second diffusion layer.

According to a further preferred development, it is provided that a basic process of the HT-N process the following, in particular temporally

successive, procedural steps comprises:

Holding at the holding temperature and the nitrogen overpressure,

Quenching in a nitrogen atmosphere to a quenching temperature, the quenching temperature preferably being 70 ° C,

- In particular freezing at a freezing temperature, wherein the

Frozen temperature is preferably between -90 ° C and -60 ° C,

- in particular tempering at a tempering temperature, wherein the

Tempering temperature is preferably between 180 ° C and 600 ° C. As a result, it is advantageously possible that the magnet armature is a martensitic

Peripheral layer and a ferrite or ferromagnetic core and / or the magnetic core (inner pole) also in the core ferritic or

ferromagnetic and in the boundary layer is martensitic. In particular, the first and / or second base material are formed as stainless ferritic rods.

According to a preferred development of the method according to the invention, the first and / or second base material is alloyed with niobium and / or titanium. As a result, it is advantageously possible to ensure more stable magnetic properties and corrosion properties even in the event of fluctuations in materials chemistry.

According to a further preferred embodiment of the solenoid valve according to the invention it is provided that a nitrogen content of the first

Diffusion layer from a surface of the first diffusion layer to a core of the first base material out, in particular steadily, decreases and / or a nitrogen content of the second diffusion layer from a surface of the second diffusion layer to a core of the second base material towards, in particular steadily decreases.

This makes it advantageously possible to realize the solenoid valve particularly cost-effective and yet with a particularly good wear resistance or with a particularly good service life stability.

Embodiments of the present invention are illustrated in the drawings and explained in more detail in the following description.

Brief description of the drawings

Show it

Figures 1 and 2 are schematic views of a solenoid valve according to an embodiment of the present invention.

Embodiment (s) of the invention

In the different figures, the same parts are always the same

Reference numerals provided and are therefore usually named or mentioned only once in each case.

Figure 1 shows schematically a sectional view of a solenoid valve 113 according to the present invention. FIG. 2 schematically shows a

Detail section of the sectional view of Figure 1. The solenoid valve 113 is in particular a fuel injection valve for liquid fuel. The solenoid valve points a valve needle 110 and a return spring 114. The magnet valve 113 is substantially rotationally symmetrical with respect to an axis 112. A magnetically soft armature 106 (also referred to below as magnet armature 106) made of a ferromagnetic material is axially displaceably mounted and is called magnet coil 103 when the coil 103 is turned on ) by the resulting magnetic force of a soft magnetic inner pole 111 (hereinafter also referred to as magnetic core 111) tightened. For a large magnetic force is to strive that the magnetic flux as completely as possible - for example, in Figure 2 shown - armature air gap 107 (between armature 106 and magnetic core 111) passes.

For this purpose, in particular a valve sleeve 105 (also referred to below as sleeve 105) in the region of the armature air gap 107 is provided with an annular groove (also referred to below as a groove or as a thin-wall region). This

Thin wall region causes due to the small residual wall thickness (the sleeve 105), a reduction of the cross section of the valve sleeve 105, so that the magnetic flux almost completely in the armature air gap 107 and not unused in the sleeve 105 runs. The valve sleeve 105 has the task to seal the interior against the environment. The fuel pressure inside the sleeve 105 is generally much greater than the ambient pressure, so that the sleeve 105 is pressurized and must absorb high radial forces.

For reinforcing the material (hereinafter referred to as base material) of the magnet armature 106 and / or the magnetic core 111 - in particular in such areas (in particular surface areas) of magnet armature 106 and / or magnetic core 111, the increased wear against rubbing or

According to the invention, it is provided that a first diffusion layer 108 is provided on the magnet armature 106 and / or that a second diffusion layer 109 is provided on the magnet core 111. According to the invention, the first diffusion layer 108 and / or the second diffusion layer 109 are produced in a high-pressure embroidering process (HT-N process).

The first diffusion layer 108 and / or the second diffusion layer 109 has, in particular, a greater wear resistance than the base material of the magnet armature 106 and / or magnetic core 111, so that the longevity of the moving relative to one another and optimized for their magnetic properties elements (ie, the armature 106 and / or the magnetic core 111) can be increased in an advantageous manner.

It can be seen in FIG. 2 that the valve needle 110 has an element 110 ', which in particular is firmly (i.e., in particular positively and / or non-positively and / or materially bonded) and thus not connected in a relatively movable manner to the base material of the valve needle 110. Opposite this member 110 'connected to the valve needle 110, the armature 106 is relatively displaceable (or relatively movable) parallel to the axial extent of the valve needle 110 (i.e.

parallel to the axis 112), wherein the relative mobility of the magnet armature 106 by two frets (denoted by the reference numeral 110 'and hereinafter also called stop collars) of the connected to the valve needle 110 member 110' is limited. The magnet armature 106 abuts during operation of the

Solenoid valve 113, however (due to its relative movement with respect to the valve needle 110 and thus also with respect to the valve needle 110 connected to the element 110 ') at the frets, wherein in this

Surface regions of the armature 106, a wear protection in the form of the first diffusion layer 108 is provided.

The second diffusion layer 109 is according to the invention in particular on

Magnetic core 111 is provided so as to cover the surface area of the magnetic core 111 opposite to the magnet armature 106 (that is, in this area covers the base material of the magnetic core 111). This area is also substantially perpendicular to the axial direction of valve needle 110 (i.e., perpendicular to axis 112). Furthermore, according to the invention, the second diffusion layer 109 is arranged in particular also in that region of the magnetic core 111, with respect to which the valve needle 110 (or an element moving with the valve needle) moves. In this area, the surface area of the magnetic core 111 is cylindrical and parallel to the axial direction of the valve needle 110.

According to the invention, it is provided in all embodiments to produce the first diffusion layer 108 and / or the second diffusion layer 109 by means of a high-pressure embroidering process. According to a preferred embodiment (not shown), the magnet armature 106 and / or the inner pole 111 is completely enveloped by the first or second diffusion layer 108, 109, wherein in particular the first and / or second diffusion layer forms everywhere where the component surface in

Contact to the oven atmosphere stands. For example, a layer only partially (i.e., not completely) enveloping the magnet armature 106 and / or inner pole 111 may be produced in a post-processing step.

Claims

claims

1. A method for producing a solenoid valve (113), in particular a fuel injection valve, with a displaceably guided in the axial direction valve needle (1 10), with a magnetic core (11 1), with a magnetic core (11 1) arranged axially opposite magnet armature

(106), wherein the magnet armature (106) on the valve needle (1 10) is arranged, wherein the magnet armature (106) comprises a first base material and the magnetic core (1 11) comprises a second base material, characterized in that in a Hochdruckaufstickprozess (HT -N process) on the first base material, a first diffusion layer (108) and / or on the second base material, a second diffusion layer (109) is generated.

2. A method for producing a solenoid valve (113) according to claim 1, characterized in that in the HT-N process, a holding time and / or a holding temperature are controlled such

- That a magnetic saturation induction of the first

Diffusion layer (108) differs from a magnetic saturation induction of the first base body by less than 20%, preferably less than 10%, more preferably by less than 1%, most preferably by less than 0.1%, and / or

- That a magnetic saturation induction of the second

Diffusion layer (109) of a magnetic saturation induction of the second body by less than 20%, preferably less than 10%, more preferably by less than 1%, most preferably by less than 0, 1%,

in particular, the structure of the first and / or second

Base material is ferritic, preferably ferromagnetic, particularly preferably ideal ferromagnetic, is set. Method for producing a solenoid valve (113) according to one of the preceding claims, characterized in that the first and / or second base material is alloyed with niobium and / or titanium.

A method for producing a solenoid valve (113) according to any one of the preceding claims, characterized in that in the HT-N process, the holding time and / or holding temperature is controlled such that the first and / or second base material in the region of the first and / or second diffusion layer (108, 109) has a Vickers hardness between 100 HV and 800 HV, preferably between 400 HV and 750 HV, more preferably between 550 HV and 700 HV.

A method for producing a solenoid valve (113) according to any one of the preceding claims, characterized in that in the HT-N process, the holding time and holding temperature is controlled such that the first and / or second diffusion layer (108, 109) has a layer thickness between 10th Micrometer and 500 microns, preferably between 50 microns and 350 microns, more preferably between 100 microns and 250 microns.

Method for producing a solenoid valve (1 13) according to one of the preceding claims, characterized in that in the HT-N process nitrogen in the first and / or second base material at a nitrogen pressure between 0 bar and 5 bar, preferably between 0.1 and 4 bar, particularly preferably between 0.5 bar and 3.5 bar and / or a holding temperature between 800 ° C and 1500 ° C, preferably between 900 ° C and 1400 ° C, more preferably between 1000 ° C and 1300 ° C. , is diffused.

Method for producing a solenoid valve (1 13) according to one of the preceding claims, characterized in that a

Basic process of the HT-N process includes the following, in particular temporally successive, process steps:

Holding at the holding temperature and the nitrogen overpressure,

Quenching in a nitrogen atmosphere on a Quenching temperature, wherein the quenching temperature is preferably 70 ° C,

in particular freezing at a deep-freezing temperature, wherein the deep-freezing temperature is preferably between -90 ° C and -60 ° C,

- In particular tempering at a tempering temperature, wherein the tempering temperature is preferably between 180 ° C and 600 ° C.

8. Solenoid valve (1 13), produced by a method according to one of the preceding claims, characterized in that the first diffusion layer (108), a first nitrogen-hardened surface of the first base material and / or the second diffusion layer (109), a second nitrogen-hardened surface of the second base material, wherein in particular the first and / or second base material comprises a steel material.

9. A solenoid valve (1 13) according to claim 8, characterized in that a nitrogen content of the first diffusion layer (108) from a surface of the first diffusion layer (108) to a core of the first

Base material out, in particular steadily, decreases and / or

Nitrogen content of the second diffusion layer (109) from a surface of the second diffusion layer (109) to a core of the second

Base material, especially steadily, decreases.