EP0733162B1 - Method of manufacturing a magnetic circuit for a valve - Google Patents

Abstract

In prior-art electromagnetically operated fuel-injection valves, a connecting ring (5) made of non-magnetic material is securely fitted between the inner pole (3) and the separately fashioned valve shell (4) to form a tight seal. The manufacture of the high-precision components and fixing the components in place until the tight, secure connection has been produced are time-consuming and costly. The method proposed for the manufacture of a magnetic circuit for a valve is a particularly inexpensive variant using the minimum of materials. The one-piece valve housing (1) has a groove (61) into which the non-magnetic ring (5) is fitted. A pressing die (68) is used to exert a longitudinally acting compressive force on the ring (5), thus displacing material in the ring (5) and in the valve housing (1) radially. Simple machining techniques are then used to remove material form the valve housing (1), starting from an opening (53), until the inner pole (3) and valve shell (4) have been formed from the valve housing (1) as physically distinct components, separated by the ring (5). The magnetic circuit thus produced is particularly suitable for valves in the fuel-injection systems of compression-type spark-ignition internal-combustion engines.

Description

State of the art

The invention is based on methods for producing a Magnetic circuit for a valve, especially for a Injection valve for fuel injection systems from 2. Internal combustion engines according to the preamble of claim 1 or 2. DE 40 13 832 A, which forms the closest prior art, is already an electromagnetic one actuatable fuel injector known in which a Connection ring made of a non-magnetic, a high specific electrical resistance material is formed that is tight and tight with an inner pole and a valve jacket of the fuel injector connected is. This ensures that between the inner pole or no fuel to the valve jacket and the connecting ring a magnetic coil that surrounds the inner pole and from which Valve jacket itself is surrounded, can reach. Since the Connection ring made of a non-magnetic material is formed, the influence of the connecting ring on the magnetic field is very low, rather it prevents a magnetic short circuit between the inner pole and the Valve jacket, and the emergence of additional Eddy current losses are avoided. Fitting the Connecting ring, however, represents a comparative represents a cost-intensive process Magnetic body made of inner pole, valve jacket and connecting ring are, for example, an inner and an outer solder ring necessary to be able to create tight and tight connections.

Thus, for example, five individual parts are used for production of the magnetic body is required. The individual components inner pole, Valve jacket and connecting ring must be manufactured very precisely be and fixed to each other before the joining process. The manufacture of the individual high-precision components and that Fix the components until the tight and fixed connections are complex and costly Method.

From also generic DE 42 30 376 C is under other for the manufacture of a valve needle for a Electrically actuated valve, metal injection molding (MIM) method known. A one-piece, from an armature section and a valve sleeve section existing actuating part according to the MIM method produced. The MIM process involves the production of Molded parts made of a metal powder with a binder, e.g. a plastic binder, for example conventional plastic injection molding machines and that then removing the binder and sintering the remaining metal powder structure. Because the composition of the metal powder in a simple way to optimal magnetic properties of the desired molded part this method cannot be coordinated only for the production of actuation parts, such as valve needles, but also for the production of magnetic circuits for Valves. The magnetic circuit is next to the solenoid and the Anchor at least from the core, intermediate ring and Nozzle carrier formed as a valve housing part.

Advantages of the invention

The inventive method for producing a Magnetic circuit for a valve, especially for a Fuel injector, with the features of claim 1 has the advantage that with less Individual components than in the prior art Magnetic body is formed. The is particularly advantageous Eliminate multiple highly accurate items by adding just one one-piece, for example extruded valve housing as Part of the magnetic body is used. The valve housing is designed so that a by the invention Process later formed inner pole and also first Valve jacket to be trained with each other due to the one-piece valve housing are connected. The From the outset, the valve housing has an outer contour, the later contours of the inner pole and the Valve jacket corresponds.

It is advantageous to have a non-magnetic, circular ring Intermediate ring in a groove provided on the valve housing to insert. The insertion of the intermediate ring is special simply because the groove defines a defined position for the Intermediate ring is specified. With a press tool, through which exerts an axially acting force on the intermediate ring an extrusion process is caused. The on the Intermediate ring force causes material flow the intermediate ring and the valve housing radially largely at right angles to the direction of action of the press tool, because in Press tool a corresponding free space for the flowing Material is provided. The material flow causes the Intermediate ring deeper into the material of the valve housing penetrates and forms a firm bond. The Establish the final spatial separation of the inner pole and valve jacket is advantageous in that it is very simple and removal of the superfluous material, for example by turning, in opening of the valve housing takes place.

The inventive method for producing a Magnetic circuit for a valve, especially for a Fuel injector, with the features of claim 2, has the advantage that a magnetic body is simple and inexpensive to manufacture. It is advantageous that in the so-called metal injection molding (MIM) method a non-magnetic intermediate ring and a magnetic valve housing in one operation a conventional plastic injection molding machine as Moldings can be injection molded. The composition of the metal powder used in each case can desired optimal magnetic properties of the Magnetic body can be matched.

By the measures listed in the subclaims advantageous developments and improvements in Claim 1 and 2 specified method possible.

It is advantageous if the intermediate ring from one non-magnetic, a high specific electrical Resistance material is formed so that the influence of the intermediate ring on the magnetic field very much is minor and the emergence of additional Eddy current loss is prevented.

Since the valve housing is in one piece from the beginning and even after the process steps according to the invention represents one-piece body with three assemblies is one the resulting pressure tightness is a particular advantage. With minimal use of fabric, it becomes a pressure-tight one Creates a magnetic circuit that does not use sealing elements, like O-rings, can be installed in the valve, so that on additional components can be dispensed with. Training of the valve housing according to the inventive method also enables a very simple construction of a Solenoid that is dry and tight from the valve body and a guide element is included and no additional Coil carrier body required.

It is advantageous if as a binder in the MIM process a plastic binder is used and if this binder by thermal treatment of the Molding is removed from this molding. In this way becomes a particularly simple manufacture of the Valve housing and molded part forming the intermediate ring enables that already has a high structural density.

It when the molded part after the Sintering is hot isostatically pressed, so that a results in a particularly dense structure of the valve housing.

drawing

Embodiments of inventive manufactured Fuel injectors or magnetic circuits are in the Drawing shown in simplified form and in the following Description explained in more detail. 1 shows it 2 designed according to the invention one-piece valve housing, Figure 3 is a one-piece Valve housing with a non-magnetic intermediate ring in one Press tool before extrusion, Figure 4 is an enlarged Representation of the extrusion area from Figure 3, Figure 5 a Valve housing with an intermediate ring after extrusion, Figure 6 shows a valve housing with an intermediate ring according to the spatial separation of inner pole and valve jacket by a Fine machining, Figure 7 one using the MIM method manufactured intermediate ring and Figure 8 a MIM method manufactured valve housing with an intermediate ring before finishing.

Description of the embodiments

The example shown in Figure 1 Electromagnetically actuated fuel injector for Fuel injection systems, for example mixture-compression-ignition internal combustion engines has a through the inventive method Production of a magnetic circuit for a valve, tubular valve housing comprising two assemblies 1 made of a ferromagnetic material, e.g. from a soft magnetic steel. The valve housing 1 represents the Application of the method according to the invention in one piece ferromagnetic pressed part with a stepped contour, as shown in Figure 2. When describing the individual process steps are also accurate Explanation of the geometry of the valve housing 1. As a result of the method according to the invention has the valve housing 1 another shape that is particularly characterized by a resulting two-part is evident. The valve housing 1 is namely now of a tubular Inner pole 3 and a still serving as housing, stepped, tubular valve jacket 4 is formed. The spatial separation of the upstream inner pole 3 and the radially outward opposite the inner pole 3 offset and downstream valve jacket 4 is among other things by pressing a non-magnetic Intermediate ring 5 achieved. Before describing the The method according to the invention should now be in a short form Description of the structure of an exemplary Fuel injector take place.

The tubular inner pole 3 has a largely constant Outside diameter and is from a solenoid 7 partially surrounded. In addition to the inner pole 3 and the solenoid 7 belong to the electromagnetic circuit of the Fuel injector an armature 8 and a cup-shaped, the magnetic coil 7 both partially radially and axially enclosing guide element 10. The magnet coil 7 is without an additional coil former between the inner pole 3, the Guide element 10, the valve jacket 4 and ultimately in Cross-section L-shaped intermediate ring 5 completely embedded.

The cup-shaped guide element 10 is replaced by an armature 8 facing away, perpendicular to a longitudinal valve axis 12 extending floor area 11 and an in Direction to the valve jacket 4 adjacent jacket area 14 formed. The cladding region 14 surrounds the magnet coil 7 completely in the circumferential direction and is at his downstream end with the valve jacket 4 by z. Legs Flare connection firmly connected. It is also possible that the jacket region 14 only partially in the circumferential direction is trained, e.g. from several temple-like Sections exists. The bottom area 11 of the guide element 10 covers the solenoid 7 at the armature 8 facing away Axial side. In the bottom area 11 there is a center through opening 17 is provided through which the inner pole 3rd runs. Especially the cup-shaped guide element 10 enables a particularly compact design of the injection valve in the Magnetic coil area 7.

All previously mentioned components of the injection valve extend concentrically to the valve longitudinal axis 12. The also concentric with the valve longitudinal axis 12 trained tubular inner pole 3 represents a Fuel inlet nozzle and thus serves the Fuel supply inside the injector.

With its lower end 13 encloses the Valve housing 1 or the valve jacket 4 in the axial direction partially a nozzle body 15. For liquid-tight Seal between the valve housing 1 and the nozzle body 15 is an annular groove on the circumference of the nozzle body 15 formed in which a sealing ring 16 is arranged. Of the cylindrical hollow armature 8 acts with the solenoid 7 and the inner pole 3 together and protrudes through Magnet line guide paragraph 18 of the valve jacket 4 and partially the non-magnetic intermediate ring 5 in the axial direction. With the armature engages around an end facing away from the magnet coil 7 8 is a holding part 19 of a valve needle 20 and is with the Valve needle 20 firmly connected. On one of the solenoid 7 facing end of the holding part 19 is one Return spring 22 with one end. With her other The return spring 22 is supported at one end in one Through hole 24 of the inner pole 3, for example pressed-in adjusting sleeve 25. The z. B. from rolled Spring steel sheet formed tubular adjusting sleeve 25 is used to adjust the spring preload on it return spring 22. The return spring 22 is endeavors to anchor 8 and those related to it Valve needle 20 in the direction of a valve seat surface 27 move.

In the nozzle body 15 is concentric with the longitudinal axis of the valve 12 a stepped, continuous flow channel 28 educated. At its end facing away from the valve housing 1 the flow channel 28 has the conical valve seat surface 27. Two trained for example as a square Guide sections 29 of the valve needle 20 are by a Guided area 30 of the flow channel 28 out; she but also leave an axial passage for the fuel free.

The valve needle 20 penetrates one with radial play Through opening 32 in a stop plate 33, the between an armature 8 facing end face 34 of the Nozzle body 15 and one of the end faces 34 opposite inner shoulder 35 of the valve jacket 4 is jammed. The stop plate 33 is used for limitation the movement of the in the flow channel 28 of the nozzle body 15 arranged valve needle 20th

The valve needle 20 faces away from the holding part 19 conical section 37 serving as valve closing part, the one with the conical valve seat surface 27 of the nozzle body 15 interacts and the opening or closing of the Fuel injector causes. To the cone Valve seat surface 27 is included in the direction of flow End channel 38 of the nozzle body 15. This end channel 38 follows downstream z. B. a spray plate 40, the at least a z. B. introduced by punching or eroding Spray opening 41 through which the fuel is hosed.

The inner pole 3 is at least partially in the axial direction and the guide element 10 through a plastic sheathing 43 enclosed. An electrical connector 45 through which the electrical contacting of the solenoid 7 and thus their excitement occurs, for example, together with the Plastic sheath 43 molded.

At its inlet end 47, it is there as Fuel inlet connector serving inner pole 3 such designed that a fuel filter 48 can be used. For this purpose, the through hole 24 upstream of the Adjustment sleeve 25 has a larger diameter than in Area of the pressed-in adjusting sleeve 25. For example by pushing into the through hole 24 of the inner pole 3, the fuel filter 48 can be mounted, with a Retaining ring 49 with a slight radial pressure on the Wall of the through hole 24 is present. The one in that Fuel injector flows through incoming fuel the fuel filter 48 in a known manner and occurs in radial direction from the fuel filter 48.

With the help of Figures 2 to 6, the individual process steps for producing a Magnetic circuit with the components inner pole 3, valve jacket 4 and intermediate ring 5 described in detail. In FIG. 2 the one-piece valve housing 1 is shown, the under other by the inventive method in the Inner pole 3 and the valve jacket 4 according to FIGS. 1 and 6 is shared. In a first step, this is Valve housing 1 made of a ferromagnetic material as a Pressed part made so that the outer contours of the later inner pole 3 and the valve jacket 4 largely can remain unprocessed. In the elongated one Valve housing 1 are already z. B. a blind hole 52nd as part of the later through hole 24 in the area of Fuel filter 48 and one on the blind hole 52 opposite side, stepped, likewise Blind hole-like opening 53 is provided. The opening 53 has at least one of them axial section 55 already has the corresponding diameter, that is necessary for the installation of the nozzle body 15 in section 55 is. The later required diameter for the anchor 8 can in the axial direction facing the blind bore 52 Section 54 of opening 53 is not immediately provided because the radially outside of section 54 remaining material partly in the following Process steps are needed. From the inner wall of the valve housing 1 in section 54 will later Magnetic line paragraph 18 formed. Because the later Valve jacket 4, ie the area of the valve housing 1 with the inner opening 53, a larger outer diameter has than the later inner pole 3, results in Radial shoulder 57 on the valve housing 1. The radial shoulder 57 forms the lower boundary surface for the space of the Magnetic coil 7, while an outer wall 58 of the inner pole 3 the inner boundary to the valve longitudinal axis 12 for the Magnetic coil 7 represents. Starting from an outer The outer surface 60 of the valve jacket 4 runs Radial shoulder 57 not as a flat surface up to the wall 58, but it is in by a along the wall 58 in Direction to section 55, but otherwise annular groove 61 interrupted, the side walls parallel run to the valve longitudinal axis 12. Section 54 of the Opening 53 extends in the direction of blind hole 52 a little beyond the radial shoulder 57 to an end face 62, so that the later valve jacket 4 completely and the later inner pole 3 only slightly axially from opening 53 to be penetrated.

In a subsequent process step, the non-magnetic, corrosion-resistant, for example from an austenitic Steel existing intermediate ring 5 along the inner pole 3 along the wall 58 inserted into the groove 61 and there filed. In Figure 3, the valve housing 1 after Introducing the non-magnetic intermediate ring 5 to see. Of the Intermediate ring 5 is now shown schematically with one in FIG illustrated tool pressed. This will be Valve housing 1 with the later valve jacket 4 in one first form-accurate die 64 used. As the real thing Press tool is a three-part sleeve-shaped Press die 65. An inner wall 58 of the inner pole 3 directly surrounding support sleeve 66 and an outer support sleeve 67 mainly perform tasks to manage an intermediate two enclosed compression sleeve 68 and to avoid the Tilting of the non-magnetic intermediate ring 5 during the Pressing process. The press ram 65 runs in a second Die 69. The individual sleeves 66, 67 and 68 have one such a width that the inner support sleeve 66 and Press sleeve 68 rest on the intermediate ring 5 while the outer support sleeve 67 to the radial shoulder 57 of Valve housing 1 is sufficient. With the compression sleeve 68 actual force for pressing the intermediate ring 5 upset. A counterforce creates one in the opening 53 retracted support stamp 70, except for one end area 72 near the end surface 62 fills the opening 53 with a precise shape. In this end area 72 the support stamp 70 has namely a smaller diameter than the opening 53 so that an annular material-free, necessary for pressing Free space 73 is formed. The free space 73 is located not only in the same axial area of the valve housing 1, but it also has approximately the same axial Extension like the intermediate ring 5.

In FIG. 4, the one in FIG. 3 is enlarged once again area marked with a circle around the intermediate ring 5 and the free space 73 shown. The arrows are there illustrate the directions in which material is moved and is pressed. With the press sleeve 68 is thus a linear acting stamp force, marked with arrows 74 is applied to the intermediate ring 5. That's why it's about extrusion is a translational one Pressure forming process. Extrusion is called cold forming carried out. Due to the given free space 73 the material flow indicated by the arrows 75 largely at right angles to the direction of the stamp force, so that from a cross extrusion can be spoken. By in the intermediate ring 5 penetrating press sleeve 68 becomes material of the intermediate ring 5 and the valve housing 1 radially postponed. The material flow is in the axial direction negligible. Material of the valve housing 1 fills after pressing the free space 73 completely.

The intermediate ring 5 also has a different contour, because Material radially in the direction of the longitudinal valve axis 12 in the Valve housing 1 is pressed so that a previously Area 77 belonging to valve housing 1, with a Dashed line is marked after the extrusion part of the intermediate ring 5. In the effective zone of the compression sleeve 68 creates a recess, whereby the intermediate ring 5 in Cross section receives an L-shape. By pressing the intermediate ring 5 and the valve housing 1 an unsolvable Received substance connection.

In Figure 5, the valve housing 1 together with the Intermediate ring 5 shown after extrusion. Doing so clearly that the intermediate ring is now L-shaped 5 to a small extent via the wall 58 in the direction protrudes to the valve longitudinal axis 12. Due to the shape of the Support stamp 70 and the completed material flow is the axial section 54 of the opening 53 in two sections 54a and 54b divided. The two sections 54a and 54b have different diameters, the im axial region of the intermediate ring 5 formed upper Section 54b has a smaller diameter than that directly related to section 55 Section 54a. The section 54b belongs in the finished Valve housing 1 at least partially for the through hole 24th

In a last process step for the production of a Magnetic circuit for a valve is the finishing of the Valve housing 1 (Figure 6). The one for installation in one Desired contours of the fuel injector Valve housing 1 are now machined Manufacturing processes such as B. rotating. So will for example by connecting the blind hole 52 with the portion 54b, the through hole 24 is made. The outer contour of the valve jacket 4 is also by Removal of material on the circumference in the desired manner changed. A particularly important step in the machining of the valve housing 1, however, represents the Forming the opening 53. By the partially radial Widen the opening width of section 54b of FIG Opening 53 to the non-magnetic intermediate ring 5 is namely a complete spatial separation of inner pole 3 and valve jacket 4 reached. During section 55 in its diameter can be left, the Section 54a completely and section 54b partially enlarged in diameter. In axial However, the direction is also increased Section 55. The contours to be achieved depend on the Dimensions of the nozzle body 15, the stop plate 33 and the Anchor 8 from. The opening 53 ultimately has an axial Length through a lower end face 79 of the inner pole 3 is limited, which continues to a small axial extent is upstream than the radial shoulder 57, but still clearly in the area of the intermediate ring 5 surrounding it.

The final assembly of the fuel injector with the one-piece manufactured according to the invention, but now two Assemblies comprising valve housing 1 and non-magnetic intermediate ring 5 takes place in a known manner.

A second example of making a magnetic circuit for a valve is shown below with reference to Figures 7 and 8 described. With the procedure now used is the metal injection molding process. This already from DE 42 30 376 C among others Production of a valve needle known metal injection molding (MIM) process involves the production of Molded parts made of a metal powder with a binder, e.g. B. a plastic binder, for example conventional plastic injection molding machines and that then removing the binder and sintering the remaining metal powder structure. The one at this Embodiment in Figures 7 and 8 compared to that in Figures 1 to 6 illustrated embodiment constant or equivalent parts are with the same reference numerals and an additional dash featured.

In Figure 7 is one of those already described Intermediate ring 5 corresponding L-shaped in cross section Intermediate ring 5 'shown. The splash of the non-magnetic Intermediate ring 5 'takes place, for example, on a conventional plastic injection molding machine in one Operation. For this, a metal powder (e.g. non-magnetic Steel) with a plastic used as a binder mixed and homogenized and to a granulate processed, that of the plastic injection molding machine provided. According to the mold is created as injection molded part of the intermediate ring 5 '.

In a subsequent step, the Plastic injection molding machine the valve housing 1 '(e.g. soft magnetic steel + binder) with the already 5 known contour on or around the intermediate ring 5 ' injection molded (Figure 8). Because of the simple and yourself tapering inwards into the valve housing 1 ' Blind hole 52 'and opening 53' is injection molding with simple stamps or sliders possible. After the injection molding is the valve housing 1 'together with the intermediate ring 5 'as a component. From the now The present injection molded part is then the components of the plastic binder by thermal Process removed, for example, under the influence of protective gas. It a metal powder framework remains largely thereafter.

To the density of the molded part from valve housing 1 'and To increase intermediate ring 5 ', the molded part, for example sintered under the influence of protective gas in a sintering device. The sintering process can also be influenced by hydrogen or be done in a vacuum. The volume now reduced valve housing 1 'is finally similar to that first embodiment of a fine machining for example by means of cutting manufacturing processes subjected. This creates a valve housing 1 ', which in the Figure 6 corresponds to valve housing 1 shown and therefore is not shown again. To the valve housing 1 'with the intermediate ring 5 'is subsequently in a known manner Fuel injector assembled.

Claims (9)

1. Method for producing a magnetic circuit for a valve, in particular for an injection valve for fuel injection systems of internal combustion engines, having a valve longitudinal axis (12), having an inner pole (3) extending concentrically to the valve longitudinal axis (12), having a magnetic coil (7) at least partially surrounding the inner pole (3), having a valve jacket (4) which partially serves as valve housing and which likewise extends concentrically about the valve longitudinal axis (12), and having a nonmagnetic, circular intermediate ring (5) preventing a direct contact of inner pole (3) and valve jacket (4), characterized in that in the first instance a unitary valve housing (1) is produced as magnetic body having an outer contour substantially corresponding to the later desired contour of inner pole (3) and valve jacket (4), thereafter the intermediate ring (5) is disposed at the valve housing (1), subsequently the valve housing (1) is disposed in a pressing tool (64, 65, 66, 67, 68, 69, 70), by which a force is applied to the intermediate ring (5), whereby material of the intermediate ring (5) and of the valve housing (1) is displaced at least partially radially in the direction towards the valve longitudinal axis (12), into a free space (73) provided within the pressing tool (70), and undergoes a substance bond, thereafter an inner opening (53) within the valve housing (1) is broadened out radially as far as the intermediate ring (5) by cutting finishing methods, in such a way that inner pole (3) and valve jacket (4) are entirely spatially separated from one another, and finally the desired contour of the valve housing (1) is produced.
2. Method for producing a magnetic circuit for a valve, in particular for an injection valve for fuel injection systems of internal combustion engines, having a valve longitudinal axis (12), having an inner pole (3') extending concentrically to the valve longitudinal axis (12), having a magnetic coil (7) at least partially surrounding the inner pole (3'), having a valve jacket (4'), which partially serves as valve housing and which likewise extends concentrically about the valve longitudinal axis (12), and having a nonmagnetic, circular intermediate ring (5') preventing a direct contact of inner pole (3') and valve jacket (4'), characterized in that, by means of the metal injection moulding method, in the first instance the intermediate ring (5') is produced from a granulate, consisting of metal powder and a binder, by injection moulding, subsequently a valve housing (1') corresponding to the later desired contour of inner pole (3') and valve jacket (4') is injection moulded on or about the intermediate ring (5') by means of the MIM method, thereafter the components of the binder are removed from the valve housing (1') and the intermediate ring (5'), thereafter the valve housing (1') is sintered together with the intermediate ring (5'), and then an inner opening (53') within the valve housing (1') is broadened out radially as far as the intermediate ring (5') by cutting finishing methods, in such a way that inner pole (3') and valve jacket (4') are entirely spatially separated from one another, and finally the desired contour of the valve housing (1') is produced.
3. Method according to Claim 1 or 2, characterized in that an austenitic steel is used as material for the intermediate ring (5, 5').
4. Method according to Claim 1, characterized in that the pressing tool (64, 65, 66, 67, 68, 69, 70) is formed from a sleeve-shaped pressing punch (65), which in turn comprises a pressing sleeve (68) and an inner supporting sleeve (66) internally delimiting the latter, and an outer supporting sleeve (67) externally surrounding the pressing sleeve (68), a first and a second die (64, 69) surrounding the valve housing (1) and the pressing punch (65) respectively, and a supporting punch (70) projecting into the opening (53).
5. Method according to Claim 4, characterized in that the actual force for pressing the intermediate ring (5) is applied by the pressing sleeve (68).
6. Method according to Claim 5, characterized in that the pressing or extrusion moulding is a translatory pressure reshaping method which is carried out cold as cold reshaping.
7. Method according to Claim 1, 5 or 6, characterized in that the material flow caused by the application of the pressing force takes place substantially at right angles to the direction of the pressing force of the pressing sleeve (68) as transverse extrusion moulding.
8. Method according to Claim 2, characterized in that the injection moulding of the intermediate ring (5') and of the valve housing (1') is carried out in one operating step on a plastic material injection moulding machine.
9. Method according to Claim 2, characterized in that a plastic material is used as binder.

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