GB2113760A

GB2113760A - I.C. engine fuel injection nozzle

Info

Publication number: GB2113760A
Application number: GB08300242A
Authority: GB
Inventors: Godfrey Greeves
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1982-01-23
Filing date: 1983-01-06
Publication date: 1983-08-10
Also published as: GB8300242D0; GB2113760B

Abstract

An outwardly opening injector includes an opening 12 having a right cylindrical wall in which is located a head 15 of a valve member. The head has a right cylindrical portion 24 which may or may not define a clearance with the wall of the opening 12 large enough to permit fuel flow therealong when the valve head is lifted from a seating 13. The body 10 has one or more flow paths formed by a drillings 25 or slots (28), Figs. 4 and 5 (not shown), which opens through the wall of the opening at a position to be progressively uncovered by the right cylindrical portion 24 of the head, as the head moves away from the seating. <IMAGE>

Description

SPECIFICATION Fuel injection nozzle This invention relates to a fuel injection nozzle for supplying fuel to an internal combustion engine, the nozzle being of the so-called outwardly opening type and including a body defining an opening in the end of the body which in use is exposed to a combustion chamber of the engine, a valve head located in the opening, the valve head being resiliently biassed into contact with a seating to prevent flow of fuel through the opening and the valve head being lifted from the seating by the action of fuel under pressure supplied to an inlet of the nozzle, thereby to allow fuel to flow through the opening.

In a known form of such a nozzle the valve and the wall of the opening define an annular clearance through which the fuel flows when the head is lifted from the seating the resulting fuel spray is of generally conical form. Some engines function in a more satisfactory manner if the fuel spray has the form of one or more jets which produce a concentrated and more penetrative spray. This form of fuel spray can be obtained using what is known in the art as an inwardly opening injection nozzle but such a nozzle is more expensive to produce and tends to be more bulky so that the problems of locating the nozzle on an engine are more severe.

It is an object of the present invention to provide a fuel injection nozzle of the kind specified in a form in which a fuel jet or jets of concentrated form can be obtained.

According to the invention in a fuel injection nozzle of the kind specified the opening has a right cylindrical wall in which is formed the entrance or entrances to a flow path or flow paths defined in the nozzle body, said flow path opening onto said end of the body, said valve head defining a right cylindrical portion which uncovers said entrance or entrances to an increasing extent as the valve head in use, moves away from the seating.

Examples of fuel injection nozzles in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a sectional side elevation of a known form of outwardly opening nozzle, Figure 2 is a view to an enlarged scale of a portion of the nozzle seen in Figure 1, and modified in accordance with the invention, Figure 3 is a part sectional view showing a further modification of the nozzle of Figure 1, Figure 4 is a view similar to Figure 2 showing a further modification and Figure 5 is a view showing a portion of a further modified form of nozzle, in position in a combustion chamber of an engine.

Referring to Figure 1 of the drawings, the fuel injection nozzle comprises a body 10 in which is formed a bore 11. The bore 11 at the end of the body which in use opens into the combustion chamber of the associated engine, is enlarged to define an opening 12 having a right cylindrical wall. The junction between the main portion of the bore and the opening 12 is of truncated conical form to define a seating 13.

Slidable within the bore is a valve member which includes a stem 14 and a head 1 5.

The main portion of the stem 1 4 defines a clearance with the bore 11 but it is provided with a fluted guide portion 15A and a portion 1 6 which is slidable within the bore 11 and which extends beyond the end of the body. The portion 1 6 carries a spring abutment 17 between which and a flange of the body, is located a coiled compression spring 1 8. Moreover, the spring abutment is maintained against axial movement relative to the stem by means of a retainer member 1 9. The body defines openings 20 through which fuel can flow into the annular clearance between the stem of the valve member and the bore 11 and in practice, the openings communicate with a fuel inlet defined in a casing which is in sealing engagement with the flange on the body.

The head 15 of the valve member has a right cylindrical portion 21 and a first tapered portion 22 followed by a further tapered portion 23. The junction of the tapered portions 22 and 23 makes line contact with the seating when the valve head is in the closed position. In the example of Figure 1 which as mentioned is a known form of the nozzle, an annular clearance exists between the wall of the opening 12 and the wall of the right cylindrical portion 21 and as a result, when the head is lifted from the seating by the action of fuel under pressure, fuel flows through the annular clearance to produce a generally conical spray.

Turning now to Figure 2, the valve head 1 5 has a right cylindrical portion 24 which has a diameter such that there is substantially no clearance between it and the wall of the opening 12 however, the valve body defines in the particular example, two flow paths 25 which are formed by drillings in the valve body. The entrances to the drillings open onto the right cylindrical wall of the opening 1 2 at a position so that they are covered by the right cylindrical portion 24 of the valve head when the latter is in the closed position. As the valve member moves to the open position the entrances to the drillings 25 are progressively uncovered and fuel can flow through the drillings to form concentrated jets or sprays 26 of fuel.

These sprays have an increased penetrative power as compared with the form of spray obtained from the nozzle shown in Figure 1. The entrances to the drillings are progressively uncovered as the pressure of fuel increases however, it may be difficult to obtain a spring which can provide the required increase of force over the small movement of the valve head and hence it may be necessary instead of providing a single drilling 25 to produce at least two axially spaced drillings 27 as shown in Figure 3. The spacing between the drillings can be increased so that an appreciable increase in the spring force is obtained as the valve head moves to uncover the drillings. In the particular example each drilling is 0.2 mm and when both drillings are uncovered it is equivalent to a single drilling of 0.28 mm both these measurements referring to the diameter of the drillings.

As shown, the axes of the adjacent drillings 27 are parallel but if desired the axes may converge so that a single spray or jet is produced. Moreover because the fuel pressure tends to rise with increasing speed, at low speed the lower drilling 27 only may be uncovered. As the speed increases the upper drilling or drillings, if more are provided in the group, will be uncovered thereby giving a variable area characteristic as a function of engine speed and also load as represented by the quantity of fuel supplied to the engine. This is beneficial to the combustion of the fuel in the combustion chamber of the engine.

An alternative to the drillings is seen in Figure 4 and in this example the drillings are replaced by axial slots 28 which are formed in the end of the valve body. The slots are obturated by the right cylindrical portion of the valve head when the valve head is in the closed position. In the examples of Figures 2-4, the right cylindrical portion 24 of the valve head has a very small clearance with the wall of the opening 1 2 such that practically no fuel can flow through the annular opening. Nozzles of this type are particularly suited for use with direct injection engines which currently use four or more fuel sprays from a centrally placed injector and where it is known that a variable area characteristic is beneficial to engine performance.

In the example of Figure 5 the clearance is increased so that a generally annular spray as with the example of Figure 1, is obtained as soon as the valve head is lifted from its seating. The nozzle is also provided with a slot 28 which is uncovered by the right cylindrical portion 24 of the valve head after the valve head has moved a predetermined extent. Besides the annular spray which is generally indicated at 29, there is also obtained a spray indicated at 30 having an increased penetrative power and conveniently the spray 30 is directed in the opposite direction to the swirl of air within the combustion chamber, this being indicated by the arrow 31. This arrangement is particularly advantageous for use with indirect injection engines where the fuel is delivered to a small combustion chamber which is separate from the engine cylinder or for some types of direct injection engines which have been developed and which have very high swirl and use an injection nozzle which is offset from the axis of the cylinder.

The spray 30 is only produced when the pressure of fuel supplied to the nozzle exceeds a predetermined value generally when the engine is running at high speed. The spray 30 is abie to penetrate into the air stream which as the engine speed increases, has an increased velocity.

Claims

1. A fuel injection nozzle for supplying fuel to an internal combustion engine, the nozzle being of the so-called outwardly opening type and including a body defining an opening in the end of the body which in use is exposed to a combustion chamber of the engine, a valve head located in the opening, the valve head being resiliently biased into contact with a seating to prevent flow of fuel through the opening and the valve head being lifted from the seating by the action of fuel under pressure supplied to an inlet of the nozzle, thereby to allow fuel to flow through the opening, said opening having a right cylindrical wall in which is formed the entrance or entrances to a flow path or flow paths defined in the nozzle body, said flow path opening onto said end of the body, said valve head defining a right cylindrical portion which uncovers said entrance or entrances to an increasing extent as the valve head in use, moves away from the seating.

2. A nozzle according to Claim 1 in which said flow path is defined by a drilling in said body.

3. A nozzle according to Claim 1 in which said flow path is defined by at least two axially spaced drillings in said body.

4. A nozzle according to Claim 1 in which said flow path is constituted by an axial slot extending inwardly from the end of the body.

5. A nozzle according to Claim 1 in which said right cylindrical portions have small clearance to substantially prevent the flow of fuel therealong.

6. A nozzle according to Claim 1 in which said right cylindrical portions define an annular clearance whereby a generally annular fuel spray is also produced when the valve head is lifted from the seating.

7. A 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 Figure 1 as modified by Figure 2 of the accompanying drawings.

8. A 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 Figure 1 as modified by Figures 2 and 3 of the accompanying drawing.

9. A 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 Figure 1 as modified by Figure 4.

1 0. A 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 Figure 1 as modified by Figure 5.