GB2203193A

GB2203193A - Electromagnetic valve

Info

Publication number: GB2203193A
Application number: GB08808142A
Authority: GB
Inventors: Werner Stark
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1987-04-08
Filing date: 1988-04-07
Publication date: 1988-10-12
Also published as: KR960013106B1; FR2613810A1; KR880012888A; GB8808142D0; DE3711850A1; JPS63259280A

Description

ELECTROMAGNETIC VALVE 2203193 The present invention relates to an

electromagnetic valve, especially a fuel injection valve for a fuel injection installation for an internal combustion engine.

In a known electromagnetic valve (German (Fed. Rep.) patent specification No. 23 49 584) a head end, which is provided with annular grooves, of a valve needle is plugged into a receiving bore of an armature and fastened therein through deformation of the armature material by means of a die ring drawn over the armature.

In order to permit fluid flow past the head end in the installed state of the valve needle, the head end is provided with two axially extending surfaces which during production require deburring by grinding. Due to these axially extending surfaces at the head end, a slight eccentricity results when the armature is fitted on to the head end, so that a greater external diameter of the armature must initially be present in order for sufficient material to be available for grinding down to the final diameter. The original increased armature diameter must, however, be deformed during the pressing operation with the die ring and this leads to an impair- ment of the magnetic properties of the armature.

According to the present invention there is provided an electromagnetic valve comprising a housing, a valve needle arranged in the housing and cooperable with a valve seat, an armature which is provided with a passage bore receiving a head portion of the needle and which is secured to the head portion by material deformation, and electromagnetic means arranged in the housing and operable to displace the armature together with the valve needle relative to 1 1 the valve seat, the armature being provided in the wall of the bore with at least three substantially equidistantly spaced grooves extending in the axial direction of the bore and serving as flow passages for the flow of fluid past the head portion of the valve needle.

A valve embodying the present invention may have the advantage of ensuring a central position of the valve needle and armature after pressing, so that a smaller additional amount of the external armature diameter is needed for the pressing of the armature onto the head end of the valve needle and a smaller deformation of the armature material is thereby caused by a pressing die ring, which leads to better magnetic properties of the armature. The smaller required additional amount of the external armature diameter results in a reduction of the required time for grinding of the external armature diameter to its final dimension.

Preferably, the head portion of the valve needle is provided with at least one annular groove extending around its circumference. Preferably, also,the head portion of the needle has a knurled surface portion. The at least one annular groove at the head portion of the valve needle ensures a secure axial fixing, whilst the knurled surface portion at the head portion increases the rotational securing between the armature and the valve needle.

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a sectional view of the lower end portion of an electromagnetic valve embodying the invention; and Fig. 2 is a sectional view along the line II-II in Fig. 1.

1 Referring now to the drawings there is shown part of an electromagnetic valve comprising a valve housing 1 in which is disposed a magnet coil 3 mounted on a coil carrier 2, the valve serving as, for example, a fuel injection valve for a fuel injection system of mixture-compressing, applied ignition internal combustion engine. A ferromagnetic core 4 is disposed within the coil carrier 2 and partially surrounded by this. Arranged facing an end face of the core 4 and also partially disposed within the coil carrier 2 is an armature 5, which is connected with a metallic valve needle 6 serving as a valve closure body. A compression spring 7 bears against the armature 5 and loads this in a direction away from the core 4. Lying against a step 9, through which the armature projects, of the valve housing 1 is an abutment plate 10 having a recess 11 which encompasses a neck 12 of the needle 6 in such a manner that the armature 5 is arranged on one side of the plate 10 and an abutment collar 13, which projects radially beyond the recess, of the needle 6 is arranged on the other side. The stroke of the needle 6 on actuation thereof is determined by the axial spacing between the abutment plate 10 and the abutment collar 13.

The valve needle 6 is displaceably mounted in a metallic jet body 15, which is connected with the housing 1 (details of the connection, for example by compression of material of the housing into a groove of the jet body, are not illustrated) and presses the abutment plate 10 against the step 9. The jet body 15 has an axial guide bore 16, which terminates, remote from the magnet coil 3, in a conical valve seat 17,and an adjoining fuel outlet 18. The outlet 18 can, if desired, be dimensioned to provide a specific fuel 1 outflow rate, i.e. to meter the fuel.

The needle 6 is guided in the bore 16 of the jet body 15 and at its end remote from the magnet coil 3 has a conical portion 20, which is adjoined by a narrow sealing portion 21. The sealing portion 21 bears directly against the valve seat 17 of the jet body 15 when the injection valve is closed. For opening of the valve, the needle 6 with the sealing portion 21 lifts off the valve seat 17 and thereby frees a flow passage for fuel. The tip of the conical portion 20 may still project into the opening 18. The portion 20 can not only have the illustrated form of a cone, but can also include a needle spigot which forms a coaxial extension of the needle 6 and projects out of the opening 18.

The valve needle 6 also has a cylindrical portion 23 adjoining the sealing portion 21 and two axially spaced guide portions 30 and 15- 31, which provide guidance of the needle 6 in the bore 16. The guide portions 30 and 31 are provided at their cirumferences with flats 33 forming throughflow openings, these flats giving the guide portions, for example, a four-cornered cross-section.

The guide bore 16 of the jet body 15 is stepped, in a region remote from the magnet coil 3, to form an enlargement 35 which is required for production technique. The diameter of the enlargement, which effectively is an undercut, is greater than the diameter of the bore 16. The above-mentioned valve seat 17 adjoins the enlarge ment 35.

Between the guide portions 30 and 31 the valve needle 6 has a connecting portion 40 which is reduced in diameter compared with the guide portions and which together with the wall of the bore 16 i 1 bounds an annular flow channel 41.

The needle 6 is provided on its neck 12 with a head portion 44 of circular cross-section, the head portion projecting into a stepped receiving bore 45 of the armature 5 and being secured therein by pressing. Starting from the.armature end face 46 facing the valve seat 17, the bore 45 has a retaining portion 48 and then a throughflow portion 48 of smaller diameter, which opens into a seating bore 50 receiving and guiding the compression spring 7. The bore 50 opens at the oppositely disposed armature end face 49. The receiving bore 45 extends concentrically with the armature external circumference. Extending from the armature end face 46 are at least three axial grooves 52 (see also Fig. 2), which so extend in axial direction within the armature 5 around the head portion 44 of the needle 6 that they are open to the bore 45 and ensure a flow connect- ion from the armature end face 46 to the throughflow portion 48. Illustrated by way of example in Fig. 2 are three such axial grooves 52, which have approximately the same spacing from each other. The head portion 44 can also have at least one annular groove 53 and be provided with a knurling 54. The production of the armature, which consists of soft magnetic material, can be effected by, for example, pressing, wherein the bore 45 and the grooves 52 are also formed. At the time of production, the armature 5 has a greater external diameter than its final diameter. For the connection of the needle 6 with the armature 5, the head portion 44 is pushed into the retaining portion 47 of the bore 45, with good centring being provided by the three wall regions of the portion 47 left between the grooves 52. When needle 6 and armature 5 are disposed in the intended postion relative to each other, then as described in German (Fed. Rep.) patent specification No. 23 49 584 the armature material is pressed inwardly by means of a die ring drawn over the armature and in that case encloses the head portion 44 and flows into the. groove 53. The knurling 54 provides an increased protection against rotation. Finally, the armature 5 is ground to its final external diameter. In this case the time involved is substantially reduced, compared with the prior art, in view of the smaller required additional dimension of the armature diameter. Fluid flow through the armature is ensured by the axial grooves 52 which extend around the head portion 44 in the bore 45 1 .I 1 %i

Claims

An electromagnetic valve comprising a housing, a valve needle arranged in the housing and co-operable with a valve seat, an armature which is provided with a passage bore receiving a head portion of the needle and which is secured to the head portion by material deformation, and electromagnetic means arranged in the housing and operable to displace the armature together with the valve needle relative to the valve seat, the armature being provided in the wall of the bore with at least three substantially equidistantly spaced grooves extending in the axial direction of the bore and serving as flow passages for the flow of fluid past the head portion of the valve needle.
2. An electromagnetic valve as claimed in claim 1, wherein the head portion of the valve needle is provided with at least one annular groove extending around its circumference.
3. An electromagnetic valve as claimed in either claim 1 or claim 2, wherein the head portion of the needle has a knurled surface portion.
4. An electromagnetic valve substantially as hereinbefore described with reference to the accompanying drawings.
5. A fuel injection installation for an internal combustion engine, the installation comprising an electromagnetic valve as claimed in any one of the preceding claims and arranged to serve as a fuel injection valve.

Published 1988 at The Patent 0Mce State House, 66171 High Holborn, London WC1R 4TP. Further copies may be obtained from The Patent office, Sales Branch, St Mary Cray, Orpington, Kent BRS 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent. Con. 1187.

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