GB2177159A

GB2177159A - Fuel injection nozzle

Info

Publication number: GB2177159A
Application number: GB08614168A
Authority: GB
Inventors: Geoffrey Leslie Heathcote; Keith Edwin Horne
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1985-06-26
Filing date: 1986-06-11
Publication date: 1987-01-14
Also published as: IT8620896A0; GB8516127D0; DE3620494A1; JPS62662A; ES8705087A1; GB8614168D0; FR2584143A1; ES556374A0; BR8602920A

Abstract

A fuel injection nozzle for supplying fuel to a compression ignition engine includes a valve member which is lifted by fuel pressure from a seating against the action of a spring. The lifting of the valve member is sensed by a transducer 24 which has a stator 25 of hollow cylindrical form and an armature 26 connected to the valve member. A winding 33 surrounds a part of the magnetic circuit which includes the stator and armature and the portion 35 of the armature which enters the stator is tapered so as to ensure a substantial change in the reluctance of the magnetic circuit irrespective of the production tolerances of the various components, thereby obviating the need for adjustment devices. Alternatively, the tapered portion may be formed on the stator 25, the recess being formed in the armature 26. Instead of a tapered portion being provided on the member which enters the recess, the mouth of the recess may be tapered. <IMAGE>

Description

SPECIFICATION Fuel injection nozzle This invention relates to a fuel injection nozzle for an internal combustion engine and of the kind comprising a nozzle body, a fuel pressure actuated valve member slidable in a bore in the body, resilient means biasing the valve member to a closed position, a fuel inlet and a fuel outlet in the body, said valve member when urged from the closed position by the action of fuel under pressure supplied through said inlet, allowing fuel flow through said outlet.

It is necessary for accurate control of the timing of delivery of fuel to an engine, to provide a signal indicative of the instant at which the valve member is lifted by the fuel pressure. It has been proposed to incorporate in the nozzle an electrical transducer, and many examples of transducer are known in the art.

One such example is shown in German published specification 0S3227989 and comprises a cylindrical armature which is coupled to the valve member so as to be moveable therewith, a stator member defining a cylindrical recess into which the armature can move and a winding surrounding a part of the magnetic circuit. In the closed position of the valve member, the armature is positioned so that its end surface is substantially coincident with the end of the recess, so that as the valve member lifts from the seating there will be a substantial change in the reluctance of the magnetic circuit which change can be detected by associated electronic circuitry connected to the winding.In view of manufacturing tolerances in tne various parts of the nozzle, it is necessary to adjustably mount the stator member so that it can be correctly positioned relative to the armature, so as to obtain the maximum change in the reluctance value as the valve member lifts from the seating. The provision of adjusting means for the stator member and the need to use the adjusting means in order to take account of manufacturing tolerances, adds to the cost of constructing the nozzle.

The object of the present invention is to provide a fuel injection nozzle of the kind specified in an improved form.

According to the invention a fuel injection nozzle of the kind specified comprises transducer means including a stator member and an armature member formed from magnetic material, said stator member being located in the nozzle body and the armature member being movable with the valve member, one of said members defining a recess into which the other member is moved as the valve member is lifted from its seating, a winding surrounding a part of the magnetic circuit defined by the members, the opening portion of said recess or the initial portion of the other member which enters said recess, being shaped so that the variation of the reluctance of the magnetic circuit as said other member moves into the recess defined by said one member, takes place over a range of relative movement of the members sufficient to cater for the manufacturing tolerances of the nozzle.

An example of a fuel injection nozzle in accordance with the invention will now be described with reference to the accompanying drawing in which: Figure 1 is a part sectional side elevation of a fuel injection nozzle; and Figure 2 is a view to an enlarged scale of part of the nozzle seen in Figure 1.

Referring to the drawings, the nozzle comprises a body 10 of generally cylindrical form and which at one end defines a fuel inlet 11, the inlet 11 being connected in use to the outlet of a fuel injection pump. The opposite end of the body is provided with a peripheral screw thread for engagement by a cap nut 12 in the base portion of which is formed an opening through which can extend part of a nozzle assembly 13, the assembly including a slideable fuel pressure actuated valve member 14 which is biased into contact with a seating by means of a coiled compression spring 15.

The compression spring 15 is housed within a chamber 16 defined in the nozzle body. One end of the spring 15 is carried by a spring abutment 17 which is mounted on the reduced end portion of the valve member 14 and the other end of the spring 15 bears against a shim 18, the latter engaging an amnular pole piece 19 to urge same against a step 20, defined at the end of the chamber 16. A passage (not shown) extends from the imlet 11 through a distance piece 21 positioned between the nozzle assembly 13 and the nozzle body, and through a passage in the nozzle assembly, so that fuel under pressure can act on the valve member 14 to lift the valve member from the seating and to allow fuel flow through an outlet defined ih a nozzle tip 22.The chamber 16 is provided with a drain connection 23 whereby fuel which leaks past the working clearance defined between the valve member 14 and the wall of the bore in which it is located, can escape from the chamber.

In order to be able to detect when the valve member is lifted from its seating, transducer means generally indicated at 24 is provided.

The transducer means includes a stator member 25 of cylindrical form and an armature 26.

The armature and the stator member are formed from magnetic material and the armature is mounted at the end of an extension 27 of the spring abutment 17. The stator member 25 defimes a cylindrical recess 28 and it defines a projection 29 which is slidably accommodated within a blind bore 30. The stator member is biased into contact with a step 31 formed in the internal peripheral surface of a former 32 which is slidably accommodated within a reduced portion of the chamber 16, the bore 30 forming a further extension of this chamber. The former is provided with a peripheral groove in which is located a winding 33 and the former is located in engagement with the pole piece 19 and is located about a tubular spigot defined thereby. The pole piece is formed from magnetic material and the nozzle body 10 forms a flux path between the pole piece 19 and the extension 29 on the stator.The stator member 25 is biased into contact with the step 31 by means of a coiled compression spring 34 located between the extension 29 and the blind end of the bore 30, the former also being urged into engagement with the pole piece by the spring.

The end surface of the armature 26 is generally flat but the end portion of the armature, i.e. that portion which can enter the recess 28 defined by the stator, is provided with a tapered side wall as indicated at 35.

The actual dimension of the tapered portion is sufficient so that after the components have been assembled, there is, in spite of the various manufacturing tolerances of the components forming the nozzle and the transducer means, a substantial change in the reluctance of the magnetic circuit as the valve member is lifted from its seating. It is, therefore, unnecessary to provide for external adjustment of the stator member once assembly of the nozzle and transducer means has taken place.

As shown, the taper is formed on the armature. It can, however, with equal effect, be formed at the mouth of the recess 28 in the stator member with the armature having a flat end face. Alternatively, the recess may be formed in the armature with the stator mem ber being shaped im a manner similar to the armature of the example shown in Figure 2.

As with the modification to Figure 2, the recess formed in the armature may have a ta pered entrance portion with the stator member having a flat end.

As stated the spring 34 in the example shown acts to maintain the stator member 25 in contact with the step 31 and in turn to maintain the former 32 in contact with the pole piece 19. The ingress of fuel into the winding is prevented by "O" ring seal mem bers disposed between the stator and former and between the wall of the chamber and the exterior surface of the former adjacent the pole piece 19.

Claims

1. A fuel injection nozzle for an internal combustion engine of the kind comprising a nozzle body, a fuel pressure actuated valve member slidable in a bore in the body, resili ent means biasing the valve member to a closed position, a fuel inlet and a fuel outlet in the body, said valve member when urged from the closed position by the action of fuel under pressure supplied through said inlet, allowing fuel flow through said outlet, transducer means including a stator member and an armature member formed from magnetic material, said stator member being located in the nozzle body and the armature member being movable with the valve member, one of said members defining a recess into which the other member is moved as the valve member is lifted from its seating, a winding surrounding a part of the magnetic circuit defined by the members, the opening portion of said recess or the initial portion of the other member which enters said recess, being shaped so that the variation of the reluctance of the magnetic circuit as said other member moves into the recess defined by said one member, takes place over a range of relative movement of the members sufficient to cater for the manufacturing tolerances of the nozzle.

2. A fuel injection nozzle according to Claim 1 in which the shaped portion is tapered.

3. A fuel injection nozzle according to Claim 2 including a chamber defined in the nozzle body, a step defined in the chamber, an annular pole piece located against said step, an annular former located in a reduced portion of the chamber and carrying said winding, said armature member extending through said pole piece and within said former, said stator member being located within said former and having an extension which is slidable within a blind bore formed in the end wall of the chamber.

4. A fuel injection nozzle according to Claim 3 including a spring located in said bore, said spring acting to urge the stator member into engagement with a step formed in the internal peripheral surface of the former and acting to urge the former into engagement with the pole piece.

5. A fuel injection nozzle according to Claim 4 in which said pole piece is held against the step in the chamber by the force exerted by the resilient means which boases the valve member to the closed position.

6. A fuel injection nozzle according to Claim 3 in which said winding is located within a groove formed in the outer peripheral surface of the former, the nozzle further including seal members disposed between the stator member and the inmer peripheral surface of the former and between the outer peripheral surface of the former and the wall of the reduced portion of the chamber respectively, the seal members acting to prevent the ingress of fuel into the winding.

7. A fuel injection nozzle comprising the combination and arrangement of parts sub stantially as hereinbefore described with refer ence to the accompanying drawings.