GB2158151A

GB2158151A - Fuel injection nozzles

Info

Publication number: GB2158151A
Application number: GB08508343A
Authority: GB
Inventors: Godfrey Greeves
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1984-04-26
Filing date: 1985-03-29
Publication date: 1985-11-06
Also published as: JPS60240871A; IT8520418A0; DE3513080A1; GB8410749D0; FR2563581A1; GB8508343D0; IT1184757B

Abstract

A fuel injection nozzle for supplying fuel to an internal combustion engine includes a valve member 14 housed in a bore 11 in a nozzle body 10. The valve member is biased into contact with a seating 12 and downstream of the seating the valve member has a cylindrical valving portion 16 which is slidable in a substantially cylindrical portion 13 of the bore from which extends an outlet drilling 17. The entrance to the drilling 17 is uncovered by a valving edge 22 as the valve member is lifted from the seating and the valving edge is defined by the cylindrical surface of the valving portion 16 and a further surface 24 on the valve member. The inclination of the further surface relative to the axis of the drilling is such that when the entrance to the drilling is partly open the fuel flowing through the drilling has a free surface separated from the wall of the drilling whereby the fuel pressure energy loss in the drilling is minimised. The valve member may open in the direction of fuel flow. (Fig. 4). <IMAGE>

Description

SPECIFICATION Fuel injection nozzles This invention relates to liquid fuel injection nozzles for supplying fuel to internal combustion engines, the nozzles being of the kind comprising a nozzle body defining a bore, a fuel pressure actuated valve member slidable in the bore, said bore including a cylindrical portion from which extends an outlet drilling leading to the exterior of the nozzle body, the valve member including a cylindrical valving portion slidable in said portion of the bore, said valving portion defining a valving edge which as the valve member is moved by fuel under pressure, uncovers the entrance to said drilling to a space within the nozzle body which contains fuel at high pressure.

A nozzle of the aforesaid kind can be of the so-called inwardly or outwardy opening type and the extent the valve member moves depends upon the fuel pressure which in turn varies with the engine speed and the rate of fuel delivery to the engine. The fact that the area of the inner end of the drilling depends upon the position of the valve member allows the nozzle to adapt automatically to varying engine speeds and fuel delivery rates. For example, at low speeds a small area is required and at high speeds a larger area, to properly match the resulting fuel spray with engine speed. However, the cross-sectional area of the drilling is fixed and has to be sufficiently large to provide the required fuel spray at high engine speeds and high delivery rates.Although the entrance area can be reduced by the valve member the advantages which in theory derive from this will not be realised if the fuel flow conditions along the drilling are such as to substantially reduce the fuel pressure energy of the fuel as it flows along the drilling. If the energy of the fuel is lost, then the atomization of the fuel when it leaves the drilling will be impaired.

The object of the present invention is to provide a nozzle of the kind specified in a simple and convenient form.

According to the invention in a nozzle of the kind specified said valving edge is defined by the wall of the said cylindrical valving portion and a surface, said surface forming part of the boundary wall of said space, the angle between said surface and the longitudinal axis of the drilling being such that fuel flowing into said drilling when the entrance to the drilling is only partly open, will break from said edge to form a fuel column in said drilling, the fuel column having a free surface in said drilling.

Examples of fuel injection nozzles in accordance with the invention will now be described with reference to the accompanying drawing in which: Figure 1 is a part sectional diagrammatic representation of one example of the nozzle, Figure 2 is a view to an enlarged scale of the end portion of the nozzle with the valve member of the nozzle in the closed position, Figure 3 is a view similar to Fig. 2 showing the valve member in a partly open position, and Figure 4 is a view to an enlarged scale of a portion of an outwardly opening nozzle.

Referring to Figs. 1-3 of the drawings the nozzle includes a body 10 in which is defined a bore 11. The bore tapers inwardly to define a seating 1 2 and terminates in a cylindrical portion 1 3 which preferably is of right cylindrical form but which can taper very slightly inwardly towards the end wall of the bore. Slidable in the bore is a valve member 14, the portion of the valve member intermediate an enlargement 1 A of the bore and the seating beil.6 of reduced diameter. The enlargement in use communicates with the outlet of a high pressure fuel injection pump 9 driven in timed relationship with an associated engine.

The valve member is shaped for co-operation with the seating 12 and is biased into contact with the seating by means of a coiled compression spring 8. The clearance between the reduced portion of the valve member and the bore is referenced 1 5 and fuel can flow along this clearance when the valve member is lifted from its seating by the action of fuel under pressure.

The valve member has at its end remote from the spring, a cylindrical valving portion 1 6 which preferably is of right cylindrical form and which forms a fuel tight seal with the portion 1 3 of the bore.

Extending from the wall of the cylindrical portion 1 3 of the bore is, in the particular example, a pair of outlet drillings 1 7. These are inclined to the axis 18 of the nozzle which axis coincides with the longitudinal axis of the bore and valve member. As shown in the drawings, the inclination is not the same and the particular inclination is chosen with the configuration of the combustion chamber of the associated engine in mind. The inner ends of the drillings in the closed position of the valve member as shown in Fig. 2, are covered by the valving portion 1 6 of the valve member. A space 1 9 is defined at the end of the bore and this space communicates by way of a central drilling 20 and side drillings 21, with the portion of the bore downstream of the seating.

When fuel under pressure is supplied to the annular clearance 1 5 the fuel pressure acts upon a differential area of the valve member to lift the member against the action of the spring, away from the seating 1 2 and when such movement has occurred fuel flows from the clearance 1 5 into the space 1 9 by way of the drillings 21 and 20. Appreciable movement of the valve member must occur before the inner ends of the drillings 1 7 are unco vered but when uncovered fuel flows through the drillings and atomizes as it leaves the drillings.

As shown in Fig. 3, the valve member is partially operand the nozzle is said to be of the variable area type. The advantage is that the effective size of the entrances of the drillings varies with the axial position of the valve member and this conveniently varies with the speed and the aipunt of fuel being delivered to the engine. In order to ensure good atomization of the fuel when the areas of the entrances to the drillings are small, it is necessary to ensure that the velocity of the fuel as it flows along the drillings is maintained. In order to achieve this it is necessary that the valving edges 22 are of the correct shape so as to ensure that the fuel breaks from the edges and in flowing along the drillings 17, forms a free surface 23 (Fig. 3).

The valving edge 22 is formed by the right cylindrical portion 16 of the valve member and a surface 24 which is formed at the end of the valve member and which has an angle relative to the axis 1 8 of the valve member which is slightly less than the angle of the drilling. In Fig. 2, the angle of the drilling 1 7 is represented by the letter J and the angle of the surface 24 by the letter H. It is found that satisfactory results can be obtained providing the angle H is less than the angle J. The surface 24 is formed by a simple turning operation. In the case where the angles of the two or even more drillings 1 7 are different then the angle H of the surface 24 is chosen to suit the drilling having the smallest angle J.

As described the nozzle is an inwardly opening nozzle. It is however possible to apply the invention to an outwardly opening nozzle where as shown in Fig. 4, the valve member 25 has a head 26 of right cylindrical form at its outer end which uncovers the inner ends of drillings 27 formed in the valve body 28 as it moves outwardly from engagement with a seating towards its fully open position. The head 26 defines a valving edge 29 which is formed at the junction of the cylindrical wall of the valve member and an annular surface 30. The angles H and J are again indicated in Fig. 4 but since it is an outwardly opening nozzle the angles are indicated relative to a plane normal to the axis of the nozzle. The aforesaid space is defined by the reduced portion of the head downstream of the seating.

Claims

1. A liquid fuel injection nozzle for supplying fuel to an internal combustion engine comprising a nozzle body, a bore defined in the body, a fuel pressure actuated valve member slidable in the bore, said bore including a cylindrical portion from which extends an outlet drilling leading to the exterior of the nozzle body, the valve member including a cylindrical valving portion slidable in said portion of the bore, said valving portion defining a valving edge which as the valve member is moved by fuel under pressure, uncovers the entrance to said drilling to a space within the nozzle body which contains fuel at high pressure, said valving edge being defined by the wall of said cylindrical valving portion and a surface, said surface forming part of the boundary wall of said space, the angle between said surface and the longitudinal axis of the drilling being such that fuel flowing into said drilling when the entrance to the drilling is only partly open, will break from said edge to form a fuel column in said drilling, the fuel column having a free surface in said drilling.

2. A nozzle according to Claim 1 in which said nozzle is of the inwardly opening type said space being defined at the end of said cylindrical portion of the bore, passages in said valve member through which fuel can flow to said space, a seating defined in said bore, the valve member being shaped for cooperation with the seating, said valve member in the closed position co-operating with said seating to prevent fuel flow through said passages.

3. A nozzle according to Claim 2 in which said valving edge is defined by the cylindrical surface of said valving portion and a further surface formed on the end of the valve member, said further surface being inclined at an angle relative to the axis of the nozzle which is slightly less than the angle of the drilling relative to said axis.

4. A nozzle according to Claim 1 in which the nozzle is of the outwardly opening type the valve member defining a head of cylindrical form which uncovers the entrance to the drilling said valving edge being defined by the cylindrical surface of the valve head and a further surface defined on the valve head, said further surface being inclined at an angle relative to a plane normal to the axis of the nozzle which is slightly less than the angle of the drilling relative to said plane.

5. A nozzle according to Claim 3 or Claim 4 in which said further surface is of annular form.

6. A liquid fuel injection nozzle for supplying fuel to an internal combustion engine comprising the combination and arangement of parts substantially as hereinbefore described with reference to Figs. 1, 2 and 3 of the accompanying drawings.

7. A liquid fuel injection nozzle for supplying fuel to an internal combustion engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Fig. 4 of the accompanying drawings.