Injection nozzle

#The invention relates to an injection nozzle for use in controlling fluid flow through an outlet. In particular, but not exclusively, the invention relates to an injection nozzle for use in a fuel injector for delivering fuel to an internal combustion engine.

#FIG. 1 shows an enlarged view of a conventional injection nozzle of a fuel injector comprising a valve needle 10 which is movable within a blind bore 12 provided in a nozzle body 14. A region of the valve needle 10, having a diameter 10a, is engageable with an annular valve seating 16 defined by a portion of the bore 12 to control fuel delivery through a set of outlet openings 18 provided in the nozzle body 14. In use, when the valve needle 10 is moved in an upward direction in the illustration shown away from the valve seating 16, fuel within a delivery chamber 19, defined by the bore 12 and the outer surface of the valve needle 10, is able to flow past the valve seating 16 and out through the outlet openings 18 into an associated engine cylinder or other combustion space.

#The valve needle is provided with a compression spring (not shown) which serves to urge the valve needle against the valve seating 16 to prevent fuel injection through the outlet openings 18. Movement of the valve needle 10 away from the valve needle seating 16 to commence fuel injection may be controlled in several ways. For example, the pressure of fuel supplied to the delivery chamber 19 may be increased until such time as the force applied to the thrust surfaces (not shown) of the valve needle 10 is sufficient to overcome the spring force, thereby causing the valve needle 10 to be urged away from the valve seating 16 to permit fuel delivery through the outlet openings 18.

#Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

#FIG. 1 is an enlarged view of a conventional fuel injector, including a valve member; and

#FIG. 2 is an enlarged, exaggerated view of a valve member in accordance with an embodiment of the present invention.

#Referring to FIG. 2, there is shown a valve member 20 for use in an injection nozzle for delivering fuel to an engine cylinder, or other combustion space, of an internal combustion engine. The valve member 20 includes a first annular region 20a of substantially frusto-conical form and an end, tip region 20b, of substantially conical form, the end region 20b occupying a lower axial position along the axis 22 of the valve member 20. The end region 20b has an outer surface 26 and the first region 20a has an outer surface 24, the outer surface 24 of the first region 20a defining a seating surface 24a which is engageable with a valve seating surface 27 to control fuel delivery through outlet openings (not shown) provided in a nozzle body 25 of the injector. In an inwardly opening fuel injector, the valve seating is defined by a surface of a blind bore provided in the nozzle body, the valve member 20 being slidable within the blind bore, in use, to move the seating surface 24a into and out of engagement with the valve seating surface 27.

#The first region 20a of the valve member 20 subtends a cone angle, θ1 of approximately 61° and the end region 20b subtends a cone angle, θ2 of approximately 60°. The angular difference between the cone angle θ1 and the cone angle θ2 is therefore approximately 1°. Typically, the length, l, of the region 20a along the axis of the valve member 20 is less than or equal to 0.2 mm, but may be as great as 0.4 mm. The diameter of the annular seating surface 24g which engages the valve seating is typically 2.25 mm. The difference in angle, θ3 between the seating surface 27 and the surface 24 of the region 20a is typically 1.5°. It will be appreciated, however, that the angle θ2 may be greater or less than this, depending on the angle subtended by the seating surface 27.

#In conventional fuel injection nozzles, there is either no difference in cone angle between the end region of the valve member and the region defining the seating surface or, as shown in FIG. 1, the end region of the valve member subtends a greater cone angle than the region defining the seating surface. In the present invention, the angular difference between θ1 and θ2 being greater than θ2 ensures that the surface of the bore within which the valve member 20 is movable and against which the valve member 20 seats has an effective diameter which can be achieved with higher accuracy, and with greater repeatability, compared to known arrangements, the geometry of the valve member being such that only the seating surface 24a of the first region 20a, and not the remainder of the surface 24 or the surface 26 of the end region 20b, can seat against the end of the blind bore within which the valve member slides, in use.