GB2249134A

GB2249134A - I.C. engine fuel injector

Info

Publication number: GB2249134A
Application number: GB9122700A
Authority: GB
Inventors: Cornelis Van Rinsum
Original assignee: MTU Friedrichshafen GmbH; MTU Motoren und Turbinen Union Friedrichshafen GmbH
Current assignee: Rolls Royce Solutions GmbH
Priority date: 1990-10-27
Filing date: 1991-10-25
Publication date: 1992-04-29
Anticipated expiration: 2011-10-25
Also published as: CH684282A5; DE4034203C2; FR2668545A1; GB9122700D0; DE4034203A1; GB2249134B

Abstract

Radial arms 14 on the valve member 12 co-operate with radial grooves (15, Fig. 3) in the valve body 11 to define variable size injection orifices through which fuel flows from a chamber 22 through valve stem recesses 21 when the valve member annular surface 18 is moved from the valve seat. <IMAGE>

Description

22491-51, A FUEL-INJECTION NOZZLE FOR AN INTERNAL-COMBUSTION ENGINE The

invention relates to a fuel-injection nozzle for an internal- combustion engine with an injector needle guided in a nozzle body, a plurality of generally radially directed injection orifices in the nozzle body co-operating with the injector needle and, by varying the position of the injector needle and the nozzle body relative to each other, the size of the injection orifices is varied.

The purpose of a fuel-injection nozzle of this type is to introduce into the combustion chamber of a cylinder the variable quantities of injected fuel, which are associated with the varying load conditions of an internal-combustion engine, always with optimum jet formation.

EP 0 246 373 A1 discloses a fuel-injection nozzle of the above type, in which the nozzle body, projecting to a very great extent into the combustion chamber, is subjected to substantial thermal stress.

The constant fluidtightness of the sliding fit betweeen the nozzle body and the injector needle, which is necessary for satisfactory jet formation throughout the operating range, cannot be expected in view of the high degree of thermal stress. Moreover, in the known arrangement, the cup-shaped design of the injection nozzle end in the combustion chamber necessitates a high residual volume of fuel, which results in the undesirable dripping of fuel and carbonising of the nozzle end.

Therefore, it is the object of the invention to devise a fuel-injection nozzle for internal-combustion engines, which has steplessly controllable injection orifice cross-sections and which ensures satisfactory jet formation throughout the operating range.

The invention is characterised in that at the end of the injector needle there are a plurality of peripherally spaced, radial arms, in that the nozzle body has radial grooves, in that the arms of the injector needle are guided axially displaceably in the radial grooves of the nozzle body, and in that an annular, conical valve seat is formed from the base of the arms to the injector needle stem.

Preferably axial recesses are provided on the injector needle stem extending from the valve seat, each recess being aligned with a respective arm and having the same width.

The advantages achieved with the invention lie in particular in that, when the fuel-injection nozzle is closed, no residual volume of fuel is formed at the end of an injection operation, thereby obviating the undesirable dripping phenomenon, that no carbonising of residual fuel occurs, that the injection orifices, which are formed when the injection valve is opened, provide injection jets having approximately the same-jet energy and jet length as the otherwise conventional nozzle bores, and that the efficiency of the injection jets throughout the operating range is constantly satisfactory with large and small injection quantities.

In the accompanying drawings:

t- Figure 1 shows a partial longitudinal section of an injection nozzle taken along the line I-I in Figure 2; Figure 2 shows a cross-section of the injection nozzle taken along the line II-II in Figure 1; and Figure 3 shows a section developed corresponding to the line III-III in Figure 2.

The illustrated fuel-injection nozzle has a nozzle body 11 for mounting in the cylinder head of an internal-combustion engine and has a lower end 13 for projecting into the combustion chamber of a cylinder. An injector needle 12 is disposed axially movable inside the nozzle body 11 and can be brought into an open position by the fuel pressure against the force of a spring (not shown). The opening stroke of the injector needle 12 is adjustable by means of a device (not shown).

At the end of the injector needle 12 there are disposed four peripherally spaced arms 14 which extend radially from the injector needle stem 17 and which engage in an axially displaceable manner in corresponding radial grooves 15 forming a castellated shape at the end 13 of the nozzle body 11.

An annular conical valve seat 18 is formed from the base 16 of the arms 14 of the injector needle 12 to the injector needle stem 17, which seat co-operates fluidtightly with a corresponding countersurface of the nozzle body 11 in the closed position of the fuel-injection valve.

During the opening of the injection valve with a partial stroke 19 of the injector needle 12, 1 - 4 injection orifices 20 open between the radial grooves 15 of the nozzle body 11 and the arms 14 of the injector needle 12.

Axial recesses 21 are formed on the injector needle stem 17 extending from the valve seat 18.

Each recess 21 is aligned with a respective arm 14 and has the same width. When the injection valve is open, each recess 21 induces a streamlined deflection of the fuel from the chamber 22 into the injection orifices 20.

The inclination of the conical valve seat 18 predetermines the jet direction, the so-called elevation injection angle, for the fuel emerging from the injection orifices 20. With a view to matching the injection to the combustion chanber configuration, it is possible to determine an optimum value for the inclination of the valve seat 18.

1

Claims

A fuel-injection nozzle for an internal-combustion engine with an injector needle (12) guided in a nozzle body (11), a plurality of generally radially directed injection orifices (20) in the nozzle body (11) co-operating with the injector needle (12) and, by varying the position of the injector needle and the nozzle body relative to each other, the size of the injection orifices (20) is varied, characterised in that at the end of the injector needle (12) there are a plurality of peripherally spaced, radial arms (14), in that the nozzle body (11) has radial grooves (15), in that the arms (14) of the injector needle (12) are guided axially displaceably in the radial grooves (15) of the nozzle body (11), and in that an annular, conical valve seat (18) is formed from the base of the arms (14) to the injector needle stem (17).
2. A fuel-injection nozzle for an internal-combustion engine as claimed in Claim 1, characterised in that axial recesses (21) are provided on the injector needle stem (17) extending from the valve seat (18), each recess being aligned with a respective arm (14) and having the same width.
3. A fuel-injection nozzle for an internal-combustion engine substantially as herein described with reference to and as shown in the accompanying drawings.