GB2225810A

GB2225810A - Electromagnetic valve

Info

Publication number: GB2225810A
Application number: GB8927232A
Authority: GB
Inventors: Stefan Maier; Peter Romann; Max Greiner; Heinrich Knapp
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1988-12-06
Filing date: 1989-12-01
Publication date: 1990-06-13
Anticipated expiration: 2009-12-01
Also published as: JPH02190684A; DE3841010A1; GB2225810B; BR8906147A; GB8927232D0

Description

- 1 ELECTROMAGNETIC VALVE The present invention relates to an

electromagnetic valve.

In a known electromagnetically actuable valve (DE-OS 30 00 622), an armature is connected by way of a connecting member constructed as rod with a ball serving as valve closure body. A compression spring engages at the armature in the closing direction of the valve closure body and loads the connecting member in compression, which means that the member must be constructed with a relatively large cross-section so that it does not buckle out laterally. Moreover, it is necessary to ensure that canting of the armature and valve closure body does not take place due to slight lateral distortion of the connecting members, as this can lead to undesired impairment of the closing and opening movement of the valve body. The large cross-section of the connecting member to avoid a buckling, however, requires a relatively large mass.

Electromagnetically actuable fuel injection valves for electronically controlled fuel injection systems must, in order to meet presentday demands, have the largest possible linear function range of the quantity of fuel injected, i.e. the linear relationship in respect of the opening duration of the valve from the largest injected quantity to the smallest injected quantity must be as great as possible, i.e. more than 10:1. This problem can only be solved by using magnetic circuits of high efficiency and constructing the movable parts of the valve, thus armature, connecting member and valve closure body, to be of least possible mass. Although a fuel injection valve is known (DE-OS 21 41 264) in which a compression spring surrounds a tubular connecting member, the spring in that case bears at one end against a guide block guiding the connecting member and at its other end engages the member at about the middle third of the length thereof in valve body closing direction. That portion of the connecting member between the spring end and the valve closure body must still have a substantial wall thicknesses to accommodate the engaging spring force, so that the mass of the moved parts of the valve are still not reduced to the optimum extent.

According to the present invention there is provided an electromagnetic valve comprising a housing, electromagnetic force generating means arranged in the housing, a nozzle body provided with a valve seat, a valve closure element co-operable with the seat, an armature displaceable by such electromagnetic force and connected to the closure element by way of an elongate connecting member, and a compression spring encompassing the connecting member and acting on the closure element directly or by way of an intermediate member to urge the closure element towards the valve seat.

is A valve embodying the present invention may have the advantage that the crosssection of the connecting member can be reduced further by reason of the compression spring engaging, for example, directly at the valve closure element and thereby a reduction in the mass of the moving parts of the valve is achieved. This allows more rapid switching times to be achieved, which lead to increase in the linear operating range of the valve and a reduction in valve noise. Such a valve construction permits easy assembly and testing of the valve and thus facilitates manufacture.

It is particularly advantageous if the end of the spring remote from the valve closure element engages at a support member, which is mounted to be adjustable in axial direction of the spring so that the force of the spring in closing direction of the element can be adjusted in simple mode and manner through displacement of the support member.

It is also advantageous to provide, in the valve housing, a threaded member which is adjustable and which at its end facing the armature is provided with a non-magnetic abutment pin, the pin being provided towards the armature with an abutment protrusion forming a residual air gap. Through axial displacement of the threaded member, for example a screw, an adjustment of the desired stroke of the valve closure element may be possible without change in the residual air-gap.

Again, it is advantageous to provide, in the wall of a nozzle body carrier, at least one flow opening penetrating this wall. An adjusting device can be introduced through this opening and operable to displace the support member in its axial position in order to change the force of the spring. Consequently, the required closing force of the spring can be adjusted and the support member fixed in its position in the otherwise finally assembled state of the valve.

In one preferred embodiment, the spring bears against an intermediate member which is pivotable about a bearing surface, remote from the valve seat, of the valve closure element.

It represents a further particular advantage to construct the armature substantially in pot shape and to so fasten it to the connecting member that, by its cylindrical wall and remote from the valve closure element, it bounds an open blind bore, into which the connecting element projects with play. The connecting member end face remote from the valve closure element can then serve as an abutment on excitation of the electromagnetic force generating means. Thus, the abutment surface is not only kept small, whereby any tendency for hydraulic sticking can be reduced, but impact stressing of the armature during the attraction movement is prevented, since the aramture now no longer comes to bear against an abutment in its end settings.

With advantage, a non-magnetic abutment pin, against which the connecting member bears by the relevant end face thereof on excitation of the generating means, is firmly inserted to face the connecting member in an adjusting screw mounted to be displaceable in the valve housing.

Embodiments of the present invention will now be more particularly described by way of example only with reference to the accompanying 10 drawings, in which:

Fi 9. 3 Fig. 1 is a sectional elevation of a first valve embodying the invention; Fig. 2 is a sectional elevation of part of a second valve embodying the invention; is a sectional elevation of part of a third valve embodying the invention; and Fig. 4 is a sectional elevation of a fourth valve embodying the invention.

Referring now to the drawings there is shown in Fig. 1 a fuel injection valve for a fuel injection system of a mixture-compressing, applied ignition internal combustion engine. The valve comprises a pot- shaped valve housing 1 of ferromagnetic material, in which a magnet coil 3 is arranged on a coil carrier 2. The coil 3 has a current feed by way of an electrical plug connection 4, which is embedded in a plastics material ring partially encompassing the housing 1 at its base 9.

The coil carrier 2 sits in a coil space 6 on a core 7, which 1 extends concentrically with a longitudinal axis 8 of the valve, passes out from the base 9 of the housing 1 and projects into the coil space. The housing 1 at its open end partially encloses a nozzle carrier 10 and is tightly connected therewith. The nozzle carrier 10 has a passage bore 11. Remote from the housing 1, a nozzle body 12 with a step 13 is inserted into the bore 11 of the carrier 10 and tightly connected therewith by, for example, soldering or welding. The nozzle body 12 has a bearing rim 14 projecting radially beyond the carrier 10, on which a sealing ring 16 is arranged between the rim 14 and a retain- ing plate 15. These, too, are firmly connected with the nozzle carrier.

Facing the bore 11 of the carrier 10, the nozzle body 12 has a conical valve seating surface 18, which in the embodiment of Fig. 1 narrows towards a valve base 19 in the nozzle body. The base contains a metering bore 20 or several metering bores, which extend inclined relative to the longitudinal valve axis 8 in radial as well as tangential direction. The fuel jets issuing from the metering bores 20 are directed towards the wall of a preoaratory bore 21, adjoining the base 19, of the nozzle body 12. Lying directly against the surface 18 in the closed state of the valve is a valve closure element 23, which can be of any suitable shape and in the illustrated embodiment has a spherical portion starting out from the surface 18, an adjoining frusto-conical portion, and finally a stepped cylindrical portion with a collar 24 and a bearing surface 25 remote from the surface 18.

Encompassing the collar 24 and bearing against the bearing surface 25 of the element 23 is a compression spring 26, which loads the element in the direction of the surface 18 and at its end 27 remote from the element engages a plate 28, which is arranged to be adjustable in the bore 11 of the carrier 10. The plate 28 can, for adjustment of the closing force of the spring 26 on the element 23, be, for example, pressed into the bore 11 or have an external thread by which it is screwed into an internal thread of the bore 11. After adjustment of 5 the force of the spring 26, the plate 28 is fixed in the bore 11 by, for example, peening-over, soldering, welding or the like. Thus, a precise adjustment of the force of the spring 26 is possible by means of the plate 28. Flow openings 29 and a central opening 30, through which fuel can flow unthrottled, are formed in the plate 28 to penetrate this in axial direction. An elongate connecting member 33 is inserted in a retaining bore 32 of the valve closure element 23 and is firmly connected thereto. The member 33 can be constructed as a rod or a tube (see Fig. 2) and extends with play within the spring 26 and the central opening 30 of the plate 28 through the carrier 10.

Remote from the valve closure element, the connecting member 33 after penetration of the spring 26 and of the plate 28 ends in a retaining bore 34 of an armature 35, with which it is firmly connected. The armature 35, constructed in pot shape, is aligned with the core 7 and guided radially by a guide bore 36 in the carrierio, which adjoins the bore 11 by, for example, a step. The armature 35 has flow openings 37 for throughflow and flowing therearound of fuel, while flow grooves 38, which are open towards the guide bore 36 and permit fuel flow around the circumference of the armature 35 towards the bore 25 11, are formed in the carrier 10 in the region of the armature 35. The housing 1 in the base 9 as well as the core 7 have an adjustment opening 40, which extends in axial direction and in which an -1 - 7 adjusting screw 41 of magnetically conductive material is mounted to be displaceable. At its end facing the armature 35, the screw 41 has a blind bore 42, which is open towards the armature and into which a non-magnetic abutment pin 43 is firmly inserted. An abutment protrusion 45 projects beyond an end face 44, facing the armature 35, of the pin 43 and its axial length determines a residual air gap, since the armature bears against it in the excited state of the coil 3. In the pushed-in state of the pin 43, at least a part of the abutment protrusion 45 lies outside an end face 46 of the screw 41. The axial spacing between the armature 35 and the protrusion 45 in the non- excited state of the coil 3 represents the stroke of the armature or of the valve closure element 23, so that the stroke can be adapted to the requirements of the valve through axial displacement of the screw 41 without change in the residual air gap. After the adjustment of the stroke, the screw 41 is fixed in the opening 40 by, for example, peening- over.

The screw 41 can be operated by way of a stepped diameter access opening 49 in the ring 5. After completion of the adjusting process, the opening 49 can be closed by means of a detent cap 50, which has resilient detent elements and during assembly detents in corresponding openings in the ring 5. A ventilation bore 51 open towards the opening 49 and to atmosphere can be provided in the cap 50.

Fuel supply through the valve takes place by way of inflow openings 53, which extend through the tubular wall of the housing 1 and open into the coil space 6. The fuel supply to the openings 53 is effected by way of a fuel pressure source, for example a fuel pump. Formed between the wall of the coil space 6 and the circumference of the coil carrier 2 is an annular groove 54, by way of which the fuel can flow downwards and then in radial direction to the flow groove 38 and from there into the bore 11 in order to reach the valve seating surface. From there it is injected by way of the metering bores 20 when the valve is open. The inflow openings 53 can be associated with a sieve body 55, which is detented in the housing 1 and the sieve region of which surrounds the inflow openings 53. The body 55 also holds a further sealing ring 56 in axial position on the housing 1 between the body 55 and the ring 5.

An abutment disc 58, which like the abutment pin 43 is produced of hardest possible material, can be let into the armature 35 facing the protrusion 45 of the abutment pin 43.

In the second embodiment, shown in partial illustration in Fig. 2, similarly constructed and correspondingly functioning parts are identified by the same reference numerals as in Fig. 1. The embodiment of Fig. 2 differs from that of Fig. 1 merely in that the plate 28 is produced of sheet metal and guided and fastened by a collar 60 in the bore 11 of the nozzle carrier 10. In addition, in the embodiment of Fig. 2 the inflow openings 53 for the fuel are provided in the wall of the carrier 10 and the guide bore 36 and the flow grooves 38 are formed in the housing 1.

In the embodiment of Fig. 3, the parts constructed and functioning the same as in the previous embodiment are again identified by the same reference numerals. In this case, the nozzle body 12 has a tub- ular projection 61 extending in the direction of the housing 1 or carrier 10. The projection 61 has a fastening bore 62, which at one end thereof passes over into the valve seating surface 18 and which 1 is open at its other end. The projection 61 extends into the bore 11 of the housing 1 or of the carrier 10 and is firmly connected therewith. The plate 28, which in correspondence with the embodiment of Fig. 2 can be made of sheet metal and the collar 60 of which can be fixed in the bore 62 after adjustment of the force of the spring 26, is mounted to be displaceable in the bore 62 of the projection 61. The valve closure element connected with the connecting member 33 and the armature 35 can thus be inserted into the nozzle body 12 in a ' simple mode and manner, with the spring 26 and plate 28 already pushed onto the connecting member 33. The plate 28 is now displaced in the bore 62 until the desired force of the spring 26 is obtained. Thereafter, the plate 28 is fixed to the projection 61.

In the embodiment according to Fig. 4, parts constructed and functioning the same as in the previous embodiment are identified by the same reference numerals. In that case, in departure from the embodiments of Figs. 1 and 2, the adjusting screw 41 is mounted to be movable in an opening 40 provided only in the base 9 of the housing 1. In that case, the screw 41 fully takes over the function of a core and is surrounded by the magnet coil 3 with the coil carrier 2. The cylindrical wall of the housing 1 has at least one flow opening 64, which serves as outlet opening and is surrounded at the outside by the sieve body 55. The opening 64 communicates with the annular groove 54 surrounding the carrier 2.

The cylindrical wall of the pot-shaped armature 35 faces the screw 41 and encloses a blind opening 65, into which the connecting member 33 projects with great play. The end face 66 of the member 33 is oriented towards the abutment protrusion 45 of the abutment pin 43 and ends in the proximity Of the armature end face 67 in such a manner that a sufficiently large residual air gap remains between the screw end face 46 and the armature end face 67 when the magnet coil is excited and the connecting body end face 66 is brought into contact with the abutment protrusion 45. The end face 66 can be disposed inside or outside the blind opening 65 or can be coplanar with the armature end face 67. The armature 35 can be fastened to the connecting member 33 in'that armature material is pressed into the illustrated annular grooves of the member 33. The bore 11 of the carrier 10 is constructed to be stepped and has a smaller diameter in the immediate proximity of the armature 35 than in the proximity of the plate 28. The radial guidance of the armature 35 is provided by a guide washer 68, which is, for example, arranged in an insert opening 69 at that end of the carrier 10 which faces the housing 1, and is held by a peened-over portion 70. The armature 35 slides in a guide bore 71 of the washer 68, which can be interrupted by longitudinal grooves (not shown) so that a fuel flow path is provided between the bore 11 in the carrier 10 and the annular groove 54 in the housing 1.

Flow openings 73, which can serve as inflow openings for the fuel and which, for example, end at the bore 11 on the side of the plate 28 remote from the valve closure element 23, are provided in the wall of the nozzle carrier 10. In the present embodiment, the spring 26 does not bear directly against the element 23, but against a counterbearing 74, which is mounted to be pivotable about a bearing surface 75, remote from the valve seating surface 18, of the element 23. For this purpose, the mutually contacting surfaces of the counterbearing 74 and of the element 23 can be constructed in suitable manner, 1 1 for example part-spherically.

For adjustment of the required force of the spring 26, an adjusting device 76 in the form of a pin can be introduced through one of the flow openings 73 in the carrier 10 and, as shown in the righthand half of Fig. 4, engage in such a manner at an end face 77 of the plate 28 that the plate can be displaced until the desired force of the spring 26 is obtained. As shown in the lefthand half of the figure, an engagement groove 78, which is open towards the central opening 30 and into which an adjusting device 76, constructed in hook shape, can be introduced for the adjustment of the plate 28, could also be provided at the plate. Subsequently, the device 76 is withdrawn from the opening 73 and the plate 28 can be fixed, for example by radial peening-over of material of the wall of the carrier 10 into grooves of the plate 28. The bore 11 could also be provided with an internal thread and the plate 28 could have an external thread so that a change in axial position would also be attainable through rotation of the plate 28.

Common to all embodiments is the advantage that the spring 26 exerts no pressure force on the connecting member 33, so that its cross-section, whether a rod or tube, can be substantially less than in the case of known valves, whereby a reduction in the mass of the member 33 is achievable. Due to the reduction in the mass of the member 33, the movable mass represented by the valve closure element 23, the connecting member 33 and the armature 35, of the valve is reduced so that more rapid switching times of the valve can be achieved and valve noise reduced.

Claims

- 12 CLAIMS 1. An electromagnetic valve comprising a housing,

electromagnetic force generating means arranged in the housing, a nozzle body provided with a valve seat, a valve closure element co-operable with the seat, an armature displaceable by such electromagnetic force and connected to the closure element by way of an elongate connecting member, and a compression spring encompassing the connecting member and acting on the closure element directly or by way of an intermediate member to urge the closure element towards the valve seat.
2. A valve as claimed in claim 1, wherein the spring bears at an end thereof remote from the closure element against a support member mounted to be adjustable in the axial direction of the spring.
3. A valve as claimed in claim 2, wherein the support member is mounted in a bore in a nozzle body carrier connected to the nozzle body.
4. A valve as claimed in claim 2, wherein the support member is mounted upstream of the valve seat in a bore in the nozzle body.
5. A valve as claimed in any one of claims 2 to 4, wherein the support member comprises a plate made of sheet metal.
6. A valve as claimed in any one of claims 2 to 5, wherein the support member has a central opening through which the connecting member extends with play.
7. A valve as claimed in any one of the preceding claims, wherein the 2 connecting member is a tube.
8. A valve as claimed in any one of the preceding claims, wherein the connecting member is a rod.
9. A valve as claimed in any one of the preceding claims, wherein the armature is substantially pot-shaped.
10. A valve as claimed in any one of the preceding claims, comprising a magnetically conductive threaded member adjustably mounted in the housing and provided at an end thereof facing the armature with a blind bore receiving a fixedly mounted non-magnetic abutment Pin, the abutment pin having a portion projecting out of the blind bore and engageable with the armature to cause a residual air gao to remain between the electromagnetic force generating means and the armature.
11. A valve as claimed in claim 3, wherein the nozzle carrier is provided in a wall thereof with at least one flow opening communicating with the bore, the support member being arranged in the bore to be displaceable therealong by means of a displacing device inserted through the at least one flow opening.
12. A valve as claimed in any one of the preceding claims, wherein the spring is arranged to act on an intermediate member to urge the closure element towards the valve seat, the intermediate member being pivotable relative to the closure element about a bearing surface thereof remote from the valve seat.
13. A valve as claimed in claim 9, wherein the armature defines a blind bore open at an end face of the armature remote from the closure element, the connecting member projecting with play into the blind bore and the end of the connecting member remote from the closure element being arranged to act as an end stop on displacement of the armature by such electromagnetic force.
14. A valve as claimed in claim13, comprising a magnetically conductive threaded member adjustably mounted in the housing and provided at an end thereof facing the armature with a blind bore receiving a fixedly mounted non-magnetic abutment pin, the abutment pin being engageable with said end of the connecting member on said displacement of the armature.
15. A valve as claimed in claim 14, wherein the abutment pin projects out of the blind bore of the threaded member.
16. A valve as claimed in claim 14, wherein the abutment pin has a protrusion ending outside the blind bore of the threaded member.
17. A valve substantially as hereinbefore described with reference to any one of Figs. 1 to 14 of the accompanying drawings.
18. A valve as claimed in any one of the preceding claims, the valve being a fuel injection valve.
19. A fuel injection installation for an internal combustion engine, the installation comprising a valve as claimed in claim 18.

Published 1990 a The Patent Office. State Hmise. 66 71 High Hclb--rr.. Lc. ndon WC1R 4TP Pur, her ecp, es.-,,iaybe obtained froir. The ?a, ent Off-, ce Sales Branc-n- S: Mw.,y CraY- OrPrg'z;- - Ken- BR5 3FLE Printed b,, I=. St Mlaz; Cr-a,' Ker".- CC.r. 187 1; 1