FUEL INJECTOR

Abstract: A fuel injector for a spark ignition engine includes a central tubular core member (14) located in a body (10) housing a winding. The end face (23) of the core member is spaced inwardly from an annular flange (24) of the body. A valve member (31) is located in an opening in the flange and is attracted towards the core member when the winding is energised. The movement of the valve member is guided by a non-magnetic guide member (25) of annular form which is located about a reduced end of the core member.

Description: - 1 - "FUEL INJECTOR" This invention relates to an electromagnetically controlled fuel injector for supplying fuel to a spark ignition engine and has for its object to provide such an injector in a simple and convenient form. An example of such an injector is seen in GB214406B in which there is provided a central magnetic core member about which is wound a solenoid winding. Surrounding the winding and core member is an annular body formed from magnetic material. The body defines an inwardly extending flange which defines an annular pole face presented to and partly overlying one face of a plate valve member. The adjacent end of the core member also defines a pole face presented to the valve member and when the winding is energised the plate valve member is attracted towards the pole faces of the flange and core member. The air gaps between the flange and the valve member and the core member and the valve member and across which the magnetic flux passes, extend in the direction of movement of the valve member. In order to minimise flux leakage between the flange and the core member an appreciable radial gap must be provided and since this gap has to be bridged by the valve member the latter must be of enlarged diameter and therefore mass. In order to reduce the diameter of the valve member the diameter of the core member could be reduced but since the core member also defines the fuel inlet passage there is the possibility of magnetic saturation of the material forming the core member. According to the invention an electromagnetic injector for the purpose specified comprises a hollow cylindrical body formed from magnetic material, a tubular core member extending within the body, said core member being formed from magnetic material and being magnetically coupled to the body at one end thereof, an annular winding located within the body, and an annular flange extending inwardly from the inner surface of the body and defining an opening, said flange being located beyond the end face of the adjacent other end of the core member, an annular non-magnetic guide member located between said other end of the core member and said flange, a valve member mounted with clearance in said opening, said valve member being formed from magnetic material and being guided for movement by said guide member, a valve member mounted for movement within said guide member, said valve member being attracted towards the core member against the action of resilient means when the winding is energised and moving under the action of the resilient means into engagement with an annular seat element formed on a seat member secured within the body when the winding is de-energised, and passage means in the valve member through which fuel can flow from the interior of the core member to an outlet in the seat member when the valve member is lifted from the seat element. In the accompanying drawings:- Figure 1 is a sectional side elevation of one example of an injector in accordance with the invention. Figure 2 is a view to an enlarged scale of part of the injector seen in Figure 1, Figure 3 is a view similar to Figure 2 showing a modified form of injector. Figures 4 and 6 show modifications of the injector of Figure 2, and Figures 5 and 7 show modifications of the injector of Figure 3. Referring to Figure 1 of the drawings the injector comprises a hollow cylindrical body 10 which is formed from magnetic material and which defines an internal step 11. Located against the step is a coil former 12 upon which is wound an annular winding 13. Also provided is a core member 14 which is formed from magnetic material and which has an integral flange 15 which fits into the wider end of the body and is secured therein by a weld 16. A seal member 17 is interposed between the former 12 and the step defined between the core member 14 and the flange 15 and a further seal member 18 is located between the former and the step 11. The core member 14 extends beyond the wider end of the body to define a fuel inlet 19 and in addition, the core member is provided with a central passage 20 within which is fitted a bush 21 which serves as an abutment for one end of a coiled compression spring 22. The bush 21 is an interference fit within the bore whereby the force exerted by the compression spring can be adjusted. Turning now to Figure 2, the body defines an annular flange 24 which extends inwardly from the inner surface of the body and which is located beyond the end face of the core member. An annular guide member 25 is positioned between the flange 24 and the core member. The guide member is formed from non-magnetic material and is located about a reduced end portion of the core member. The guide member has an internal apertured flange 26 which locates against the end face 23 of the core member. Also provided is a seat member 27 which may be formed from plastics or other non-magnetic material and which is located against the flange 24 and is secured in position by means of a tubular insert 28 which extends beyond the end of the body 10 as more clearly seen in Figure 1. The seat member is provided with a central opening 29 and on its face presented to the core member there is formed an annular seat element 30 which surrounds the flared end of the opening. Located between the seat element 30 and the core member is disc-like armature 31 formed from magnetic material. The armature is located with clearance within the opening defined by the flange 24. The armature 31 is provided with a recess in its face remote from the seat member, the recess serving to locate the end of the spring 22 and in addition a deeper recess 32 is also formed in the face of the valve member, the latter also being provided with passage means extending from the recess 32 and opening onto the opposite face of the valve member at a position or positions lying outside the seat element 30. As shown in Figure 2 the passage means comprises passages 33. The valve member in the closed position as shown is partly located within the tubular guide member 25. In use, the spring 22 urges the valve member into engagement with the seat element 30 to prevent flow of fuel through the opening 29 until such time as the winding 13 is energised. When the winding is energised the flange 24 and the core member 14 assume opposite magnetic polarity and the magnetic flux flows between the inner edge of the flange 24 and the valve member across a small generally radial air gap and then from the valve member 31 to the face 23 across an air gap slightly larger in size but extending axially. An axial force is therefore developed upon the valve member and the latter moves axially against the force exerted by the spring 22 to an open position which is determined by the abutment of the valve member with the flange of the guide member 25. Once the valve member has lifted from the seat element, fuel can flow through the opening 29 and it is arranged that the fuel pressure is sufficiently high to ensure that a fuel spray is produced which since the injector is mounted in the air inlet manifold of the associated engine, is directed into the air flowing to the engine. When the winding is de-energised the armature is returned by the action of the spring into contact with the seat element 30 so that flow of fuel through the opening is halted. The guide member and its flange acts to prevent metal-to-metal contact between the valve member and the face 23 so as to avoid any tendency for the valve member to magnetically stick to the core member. As compared with previous designs in which the flange 24 terminated at substantially the same level as the end face of the core member, and the valve member was of substantially larger diameter, the smaller diameter valve member which results by adopting the construction described means that the valve member is lighter and it has been possible to reduce the contact area between the valve member 31 and the seat element 30 and also between the valve member and the flange 26 thereby reducing the tendency for the valve member to stick in the open and closed positions. The injector which is shown in Figure 3 differs only in the fact that the seat member 34 is provided with three orifices 35 which are equiangularly spaced about the axis of the seat member. The face of the seat member presented to the valve member is recessed so that the entrance to each orifice is defined by an annular seat element 36 which is engaged by the valve member 37. In this case the valve member 37 is provided with a central opening 38 extending between the opposite faces of the valve member. In the closed position of the valve member as shown, the seat elements 36 are obturated by the valve member and of course are uncovered when the valve member is moved away from the seat member upon energisation of the winding. The arrangements shown in Figures 4 and 5 are modifications of the arrangements shown in Figure 2 and 3 respectively, the modifications being to the valve member and the flange 24. As will be seen the underside of the flange 24 is formed with an annular recess 39 in which is located a flange 40 formed on the valve member 37. The clearance between the presented faces of the flange 40 and the base wall of the recess is slightly larger than the clearance between the valve member and the flange 26 of the guide member 25 and the aforesaid space forms an axial air gap for magnetic flux to assist the movement of the valve member when the winding is energised. Figures 6 and 7 show further modifications of the arrangements of Figures 2 and 3 and in these cases the side faces of the valve member and the flange 24 are inclined to produce an air gap, flow of flux across which will produce a force component acting in the direction to open the valve member. In the arrangement shown in Figures 4-7 the outer peripheral portion of the valve member is allowed to contact the seat members 27 and 34 in the closed position of the valve member to minimise tilting of the valve member.

Claims: CLAIMS 1. An electromagnetically controlled fuel injector for supplying fuel to a spark ignition engine comprising a hollow cylindrical body formed from magnetic material, a tubular core member extending within the body, said core member being formed from magnetic material and being magnetically coupled to the body at one end thereof, an annular winding located within the body, and an annular flange extending inwardly from the inner surface of the body and defining an opening, said flange being located beyond the end face of the adjacent other end of the core member, an annular non-magnetic guide member located between said other end of the core member and said flange, a valve member mounted with clearance in said opening, said valve member being formed from magnetic material and being guided for movement by said guide member, a valve member mounted for movement within said guide member, said valve member being attracted towards the core member against the action of resilient means when the winding is energised and moving under the action of the resilient means into engagement with an annular seat element formed on a seat member secured within the body when the winding is de-energised, and passage means in the valve member through which fuel can flow from the interior of the core member to an outlet in the seat member when the valve member is lifted from the seat element. 2. An injector according to Claim 1 in which said guide member defines an internal flange which limits the movement of the valve member towards said core member. 3. An injector according to Claim 2 in which said core member has a reduced end portion, said guide member being engaged about said reduced end portion with said flange engaging the end face of the core member. 4. An injector according to Claim 1 in which said seat member has a central opening, an annular seat element defined about said opening on the face of the seat member presented to the valve member for engagement by the valve member in the closed position thereof, said passage means in the valve member comprising a passage which extends from the face of the valve member presented to the core member to the opposite face, said passage opening onto said opposite face at a position outside the confines of said seat member. 5. An injector according to Claim 4 including a recess formed in the face of valve member presented to the core member, said passage communicating with said recess. 6. An injector according to Claim 1 in which said seat member has a plurality of openings spaced about the central axis of the seat member, annular seat elements defined about said openings respectively on the face of the seat member presented to the valve member for engagement by the valve member in the closed position thereof, said passage means comprising a central opening in the valve member. 7. An injector according to Claim 1 in which the face of said annular flange on the body remote from the core member is cut away and the valve member has a peripheral portion of complementary shape to define an air gap across which magnetic flux can flow between the flange and valve member when the winding energised, the magnetic, flux producing an axial force component to assist movement of the valve member.

Inventors: RENOWDEN PAUL STUART, RENOWDEN, PAUL, STUART
Applicants: LUCAS IND PLC, LUCAS INDUSTRIES PUBLIC LIMITED COMPANY
Application year: 1987
Main classification: F02M51
IPC codes: F02M51