GB2080416A

GB2080416A - Fuel injection nozzle

Info

Publication number: GB2080416A
Application number: GB8119127A
Authority: GB
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1980-07-16
Filing date: 1981-06-22
Publication date: 1982-02-03

Abstract

A pintle type fuel injection nozzle includes an outlet 14 through which fuel cart flow when the valve member 18 is lifted from the seating 15. The valve member carries a pin 21, 22, 23 and 24 which projects through the outlet and carries a deflector 25 of truncated conical form having a surface 32 which is disposed so that the annular jet of fuel leaving the outlet impinges on the surface to cause atomisation of the fuel. The projection has at least one flat 33 so that a portion of the jet misses the surface to provide a jet of fuel which penetrates into the central region of the spray cone. <IMAGE>

Description

SPECIFICATION Fuel injection nozzle This invention relates to fuel injection nozzles for supplying fuel to an internal combustion engine of the compression ignition type, more particularly to a so-called indirect injection type of engine in which the fuel is injected into a precombustion chamber which communicates with the associated engine cylinder by way of a passage, the nozzle being of the type comprising a body, a bore defined in the body and communicating at its inner end with an outlet, a seating defined in the bore and a fuel pressure actuated valve member slidable within the bore, the valve member being shaped for co-operation with said seating and in the closed position engaging said seating to prevent the flow of fuel through said outlet, the valve member being lifted by fuel under pressure acting on a surface of the valve member to allow fuel flow and the valve member carrying a pin which projects with clearance through the outlet.

Such nozzles are known in the art as pintle type nozzles and by shaping the end portion of the pin it is possible to vary the pattern of the spray of fuel produced by the nozzle. For example, if the outer end portion of the pin is shaped in the manner of a cone with the base of the cone removed from the valve member, then the spray pattern can be arranged to be of hollow conical form with the annular jet of fuel directed to form a wider angle of spray when it strikes the surface of the conical portion. The result is that the ability of the spray to penetrate into the chamber is reduced. This reduction of spray penetration will reduce the overall efficiency of combustion.On the other hand the wider angle spray allows some fuel to mix quickly and the noise level of an engine so equipped is lower than in the case where the annular fuel jet is not deflected by allowing it to impinge on a surface.

It is known in nozzles of the kind set forth above to shape the pin in a manner to prevent fuel flow through the outlet until the valve member has moved a predetermined extent away from the seating, and during this time to allow fuel flow through an auxiliary orifice. The fuel flow through the orifice is in the form of a jet which can penetrate into the air in the combustion chamber, and as the valve member continues to move from the seating flow of fuel takes place through the aforesaid outlet and the bulk of the fuel flow than takes place through the outlet. This form of nozzle was designed to facilitate the starting of the engine.

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

According to the invention a nozzle of the kind specified comprises a deflector carried by said pin, said deflector having a surface positioned in the annular jet of fuel flowing through said clearance, said surface being shaped so that part of said jet avoids the surface, the remaining portion of the jet being broken up on contact with said surface.

According to another aspect of the invention a nozzle of the kind specified comprises a deflector carried by the pin, said deflector having an annular surface upon which the annular jet of fuel flowing through said clearance can impinge to deflect and break up said jet, and a flat formed on said deflector whereby a portion of said jet passes the deflector without impingement.

One example of a fuel injection nozzle 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 the nozzle and also a holder; Figure 2 is a view to an enlarged scale of a portion of the nozzle seen in Figure 1; and Figure 3 is an end view of the valve member of the nozzle.

Referring to Figure 1 of the drawings the fuel injection nozzle comprises a body 10 which is provided with a flange whereby it can be secured by a cap nut 1 1 to a holder 12. The body 10 is provided with a bore 1 3 which communicates with an outlet 14 (Figure 2) which in the particular example is of right cylindrical form. The diameter of the outlet 14 is iess than that of the bore 13 and a seating 1 5 is defined adjacent the outlet.

Moreover, an annular chamber 1 6 is defined adjacent the seating and this chamber communicates by way of a passage in the nozzle body, and a further passage in the holder 12, with a fuel inlet 1 7 which in use, communicates with a fuel injection pump.

Slidable within the bore 1 3 is a fuel pressure operable valve member 18. This has a portion 19 which is shaped to co-operate with the seating and from the portion 1 9 there extends a pin generally indicated at 20, the pin extending through the outlet 1 4. The pin as shown in Figure 2, is formed in a number of sections and adjacent the portion 1 9 is a portion 21 which is of generally right cylindrical form, having a diameter which is slightly less than the diameter of the outlet. This is followed by a portion 22 of cylindrical form, but which tapers inwardly to a limited extent. This joins a further inwardly tapering portion 23 and this in turn is followed by a further portion 24 which tapers inwardly to a lesser extent than the portion 23.Finally there is formed at the end of the portion 24, a deflector 25 which is of truncated conical form. The dimensions of the various portions can be varied to suit a particular use and for example the portion 22 can be of right cylindrical form.

At its other end, the valve member carries a pin 26 which extends into an elongated chamber formed in the holder and is engaged by a push rod 27 the other end of which carries a spring abutment 28. The abutment 28 carries one end of a coiled compression spring 29, the other end of which is engaged on a further spring abutment 30 which is adjustably mounted on the holder. The chamber containing the spring is vented through an outlet 31.

Consideringthe general operation of the nozzle, when fuel under pressure is supplied through the inlet 17, a force is developed on the valve member 18 tending to move the valve member against the action of the spring 29. The valve member is lifted from the seating 1 5 and fuel can flow from the chamber 16 down the annular space defined between the outlet and the portions 21 and 22 of the valve member. When the flow of fuel to the inlet ceases, then the valve member is returned to its seating under the action ofthe spring 29.

As mentioned earlier in the specification, the nozzle is intended to supply fuel to an indirect injection engine which embodies a precombustion chamber formed in the cylinder head of the engine and which communicates with the associated cylinder, by way of a passage. During the compression stroke of the piston within the cylinder air is forced into the chamber through the opening. The air flow due to the compression is complex. It has been found that if the fuel is injected with sufficient penetration the efficiency of combustion is high but usually the noise of an engine using this type of injection, is also high.

Returning now to Figure 2 the annular jet of fuel which flows through the annular space defined between the pin and the outlet 14 impinges upon the surface indicated at 32, of the projection and fuel will be deflected at the surface to form a wide angle spray. A cioud of fuel droplets will therefore be formed which will mix rapidly with the air in the chamber to give a short ignition delay, this being the period between the start of fuel delivery and the indication of combustion of the fuel. As a result the noise level will be low. In order to ensure that fuel is delivered into the centre portion of the chamber, a pair of flats 33 are formed on the projection and as a result two sections of the annular jet of fuel leaving the outlet do not impinge upon the projection and therefore have sufficient penetrating power to penetrate into the air in the centre of the chamber. The relative positions of the flats and also their number can be varied as required.

Claims

1. A fuel injection nozzle for supplying fuel to an internal combustion engine of the compression ignition type, more particularly to a so-called indirect injection type of engine in which the fuel is injected into a pre-combustion chamber which communicates with the associated engine cylinder by way of a passage, the nozzle being of the type comprising a body, a bore defined in the body and communicating at its inner end with an outlet, a seating defined in the bore, a fuel pressure actuated valve member slidable within the bore, the valve member being shaped for co-operation with said seating and in the closed position engaging said seating to prevent the flow of fuel through said outlet, the valve member being lifted by fuel under pressure acting on a surface of the valve member to allow fuel flow, a pin carried by the valve member, said pin extending with clearance through the outlet, and a deflector carried by said pin, said deflector having a surface positioned in the annular jet of fuel flowing through said clearance, said surface being shaped so that part of said jet avoids the surface, the remaining portion of the jet being broken up on contact with said surface.

2. A nozzle according to Claim 1 in which said surface is of annular form, said deflector having a flat formed thereon so that a portion of said jet passes the deflector without impinging on said surface.

3. A nozzle according to Claim 2 in which said deflector is of truncated conical form.

4. A fuel injection nozzle comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.