Fuel injection nozzles

A fuel injection nozzle includes a valve member axially movable in a bore. The bore is in part defined by a sleeve secured within a drilling. A space is defined between the end of the sleeve and the drilling and fuel under pressure is supplied to the space by means of a groove formed in the external surface of the sleeve. The sleeve serves to support the valve member for axial movement towards and away from a seating defined in the bore and fuel can flow from the space past the valve member and seating through an outlet when the valve member is lifted from the seating.

This invention relates to a fuel injection nozzle for supplying fuel to an 
internal combustion engine and of the kind comprising a nozzle body having 
a bore formed therein, a seating defined at one end of the bore and a 
resiliently loaded valve member slidable in the bore and shaped for 
co-operation with the seating, said valve member being urged into contact 
with the seating by the resilient loading and being lifted from the 
seating by the action of fuel under pressure to allow fuel flow from an 
inlet to an outlet. 
It is conventional practice to form in the bore an enlargement which is 
connected to a fuel inlet by way of a drilling formed in the body. The 
formation of the enlargement in the bore and also the drilling pose 
manufacturing problems and in addition, the drilling since it runs 
alongside the bore, requires that the wall thickness between the wall of 
the bore and the exterior of the body must be sufficient to accommodate 
the drilling and also to provide adequate wall thickness to withstand the 
high fuel pressure. 
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 in a fuel injection nozzle of the kind specified 
said bore is defined in a sleeve mounted in an elongated recess in the 
body said sleeve terminating short of the end of the recess to define 
between the end of the sleeve and the end of the recess, an enlargement, 
the outer wall of the sleeve and the wall of the recess defining a passage 
through which fuel can flow to said enlargement from said inlet, the fuel 
under pressure in the enlargement acting upon said valve member to lift 
the valve member away from the seating.

Referring to FIG. 1 of the drawings the nozzle comprises a body 10 of 
stepped form the narrower end of the body in use being exposed within a 
combustion space of an associated engine. The nozzle body in practice is 
secured to a support member or holder by means of a cap nut and formed 
within the body is a blind bore 11 and this extends from the wider end of 
the body to adjacent the narrower end thereof. At the blind end of the 
bore there is defined a seating 12 about an outlet opening 13. 
Intermediate the ends of the bore the latter is provided with an 
enlargement 14 which communicates with a fuel inlet conveniently formed in 
the aforesaid holder, by way of an inlet passage 15. The inlet passage 15 
runs alongside the bore 11 to the wider end of the body and in use, is 
connected to the outlet of a fuel injection pump 16. 
Located within the bore is a valve member 17 which at its end adjacent the 
seating is shaped to co-operate with the seating. This end of the valve 
member also mounts an extension 18 which projects with clearance through 
the outlet opening 13. The portion of the valve member which is disposed 
between the enlargement and the blind end of the bore is of reduced 
diameter to define an annular clearance 19 which communicates with the 
enlargement 14 to permit passage of fuel from the enlargement through the 
opening 13 when the valve member is lifted from its seating. 
At its end remote from the seating the valve member is provided with a peg 
20 which carries a spring abutment 21, the latter being engaged by a 
coiled compression spring 22. The spring is mounted within a vented 
chamber defined in the aforesaid holder. In operation, fuel under pressure 
supplied to the enlargement 14 acts on the differential area of the valve 
member to create a force which acts to move the valve member against the 
action of the spring. When the force exerted by the spring is overcome the 
valve member is lifted from its seating to allow fuel flow through the 
annular clearance defined between the extension 18 and the wall of the 
opening 13. The extension is profiled to control the fuel flow through the 
opening and may also be profiled to alter the shape of the fuel spray 
and/or the rate at which fuel can flow. 
The formation of the enlargement 14 in the bore and also the passage 15 
present manufacturing problems. In addition, the fact that the passage 15 
extends alongside the bore 17 means that the wall thickness between the 
wall of the bore and the exterior of the body must be sufficiently large 
to accommodate the passage. 
The manufacturing problems are reduced by, as shown in FIG. 2, supporting 
the valve member within a bore formed in a sleeve 23 which is supported in 
a drilling 24 in the body. The bore in the sleeve is conveniently 
substantially the same diameter as the lower portion of the bore 11 which 
is formed in the same manner as hithertofore. The sleeve 23 is formed from 
a hardwearing material and the equivalent of the enlargement 14 is defined 
between the inner end of the sleeve and the step between the drilling 24 
and the bore 11. The sleeve is retained within the drilling in any 
convenient manner. For example, it may be an interference fit or it may be 
secured by some form of adhesive for example, an anaerobic adhesive. The 
sleeve can be formed from a ceramic material for example silicon nitride 
and the bore in the sleeve is machined after the sleeve has been inserted 
into the drilling. 
In order to avoid the need for a separate passage 15, the external surface 
of the sleeve is provided with grooves indicated at 25 in FIG. 3. These 
grooves communicate with a small recess 26 formed in the wider end of the 
body, the recess communicating with a passage in the aforesaid holder. The 
grooves 25 can be of any convenient section. Moreover, since in use, they 
will contain fuel at high pressure it is convenient in order to equalise 
the stress in the sleeve, to form the grooves in helical fashion. As a 
result of providing the grooves, the body can be of reduced diameter since 
it is no longer necessary to accommodate the passage 15. It also enables 
the remaining portion of the body to be formed from a material which is 
better able to withstand impact loads at the seating 12. Moreover, if the 
material forming the sleeve is formed from an electrically insulating 
material the valve member in conjunction with the seating, can be used as 
a switch to provide an indication of when the valve member is lifted from 
its seating. 
As described the nozzle is of the so-called "pintle type". It will be 
understood that the invention may be applied to a so-called "hole type" 
nozzle.