GB2294974A

GB2294974A - I.c.engine fuel injection nozzle

Info

Publication number: GB2294974A
Application number: GB9522295A
Authority: GB
Inventors: Udo Renger
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 1994-11-11
Filing date: 1995-10-31
Publication date: 1996-05-15
Anticipated expiration: 2015-10-31
Also published as: FR2726861B1; DE19539798A1; FR2726861A1; GB2294974B; GB9522295D0

Abstract

The mouth 4 is formed by a wall 6 which is rotationally symmetrical with respect to the central longitudinal axis M and on the inner surface 7 of which a seat 8 for a valve needle 2 is formed. A sleeve 3 spring-biased onto a seat 9 or integral with or connected to the nozzle body and provided with jet-forming passages 16 is arranged coaxially to the control needle 2 so that, with the needle raised from its seat 8, fuel can be fed from an annular space 10 through the passages and into the combustion space. The arrangement of the passages 16 is such that the individual jets 20 produced are generators of a hyperboloid of revolution 25 in the annular region of which the wall 6 is arranged. <IMAGE>

Description

DESCRIPTION AN INJECTION NOZZLE FOR USE IN A RECIPROCATING-PISTON INTERNAL COMBUSTION ENGINE The present invention relates to an injection nozzle for use in a reciprocating-piston internal combustion engine.

Outward- or inward-opening injection nozzles for introducing fuel into an internal combustion engine are fundamentally known. Both types are disclosed for diesel internal combustion engines with direct injection in SAE Paper 900821, for example. EP 04 60 381 B1 has disclosed an outward-opening injection nozzle of the generic type which essentially comprises a nozzle body, a control needle that can be moved axially in the latter along a central longitudinal axis, and a sleeve coaxially surrounding the said needle, both the control needle and the sleeve forming a sealing seat with the nozzle body in the region of the injection-nozzle mouth, which faces a combustion chamber. An annular storage space for the purpose of supplying fuel is formed between the sleeve and the nozzle body.After the sleeve has risen inwards from its sealing seat and the nozzle needle has been opened outwards in the direction of the combustion space, fuel is sprayed in a plurality of individual jets.

Particularly in the case of internal combustion engines of whatever kind with direct injection, the configuration of the injection-nozzle mouth which faces the combustion space is problematic because fuel evaporates in an uncontrolled manner from "dead spaces" into the combustion space towards the end of combustion. This problem is described in the above cited SAE Paper.

The aim of the present invention is to provide an injection nozzle for a reciprocating-piston internal combustion engine which does not have any dead space on the combustion-space side from which fuel could drip or evaporate in an a uncontrolled manner during and after combustion.

According to the present invention there is provided an injection nozzle for use in a reciprocating-piston internal combustion engine, which comprises a control needle which can be moved axially in a nozzle body along a central longitudinal axis, and a sleeve coaxially surrounding the said needle, both the control needle and the sleeve each forming a sealing seat with the nozzle body in the region of an injection-nozzle mouth with an annular storage space formed between the nozzle body and the sleeve, for the purpose of supplying fuel, which after the control needle has risen from its sealing seat, is sprayed by a plurality of individual jets towards a combustion space, an outlet opening at the combustion-space end of the nozzle body being surrounded by a bead which is rotationally symmetrical with respect to the central longitudinal axis and on the inner surface of which bead, which inner surface faces away from the combustion space, adjoining the outlet opening, the sealing seat of the inward-opening control needle is arranged, the sealing seat of the stationary sleeve being arranged coaxially with and directly adjacent to the sealing seat of the control needle, said sleeve being provided, adjacent to the bead, with jet-forming passages for fuel, which passages are opened when the control needle has risen from the sealing seat.

By virtue of the present invention the jetforming passages and the sealing seat of the nozzle needle ensures that, as the nozzle needle closes, the outlet cross-sections of the passages are first of all closed by the latter and the nozzle needle then comes to rest on its sealing seat. There are thus no dead spaces from which fuel could drip or dribble after the closure of the nozzle needle.

By virtue of the present invention, the injection jets in the case of this injection nozzle do not pass into the combustion space from a circle lying coaxially to the central longitudinal axis, as in the prior art, but, starting from this circle, are first of all directed inwards and leave the injection nozzle in an outward direction relative to the central longitudinal axis, crossing the injection-nozzle mouth as they do so. In order, as an advantageous refinement, to ensure optimum jet formation and avoid collision between individual fuel jets here, the passages are arranged in such a way in the sleeve that the individual jets formed by them are directed past the central longitudinal axis as they pass through the injection-nozzle mouth.The longitudinal direction of the passages is here inclined in such a way towards the combustion space that the angle between the imaginary perpendicular projection of the central longitudinal axis onto a plane parallel to this axis, in which the respective passage is located, and the imaginary extension of this passage is greater than the angle of the tapered sealing seat of the control needle and than the angle of the sealing seat of the sleeve.

A configuration which is particularly simple to manufacture can be achieved by means of a rotationally symmetrical arrangement of the passages in the sleeve such that given an imaginary rotation of the passages about the central longitudinal axis, the emerging individual jets describe a one-sheet hyperboloid of revolution, the imaginary minor axis of which lies on the central longitudinal axis and the major axis of which runs at a distance from the outlet opening towards the combustion space. In this arrangement, the bead is formed completely in the annular region of this imaginary hyperboloid of revolution. This ensures that the individual jets can be sprayed in an intersecting but non-interpenetrating manner and do not touch any parts of the nozzle mouth.

The passages can be surrounded on all sides by the sleeve and arranged adjacent to the bead in the sleeve or, alternatively, be designed as U-shaped recesses in the sealing surface, said sealing surface facing the sealing seat, of this sleeve, so that their open end is closed by the sealing seat. A combination of both passage designs is likewise conceivable, making it possible to achieve a two-stage injection nozzle.

The construction of the injection nozzle described is comparatively simple and therefore economical and has parts which can be machined essentially in rotationally symmetrical fashion. The sleeve is pushed directly onto the nozzle needle and is pressed onto its sealing seat by a spring supported against a collar of this nozzle needle. As an alternative, the sleeve and the nozzle body can be manufactured in one piece or be connected rigidly to one another. By virtue of the relatively simple geometry, care and maintenance are simple.

The angular position of the individual jets relative to the nozzle axis and hence to a combustionspace hollow in a reciprocating piston bears the abovementioned geometrical relationship to the seat angle of the nozzle needle but both can be varied to optimize the required operation.

The present invention will now be further described by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows a schematic cross-section through one embodiment of an injection nozzle constructed according to the present invention; Fig. 2 shows an enlarged view of the injectionnozzle mouth in accordance with Fig. 1; and Fig. 3 shows a section along the line III-III in accordance with Fig. 1.

An injection nozzle constructed according to the present invention is shown in the accompanying drawings and is for a reciprocating-piston diesel internal combustion engine (not shown) with direct injection. The nozzle is formed essentially by a nozzle body 1, a control needle 2 which can be moved axially in the latter along a central longitudinal axis M, and a sleeve 3 coaxially surrounding the said needle. An injection-nozzle mouth 4 at the combustion-space end of the nozzle has an outlet opening 5 and a bead 6 which is rotationally symmetrical with respect to the axis M and surrounds this opening 5. The inner surface 7 of the bead ie the surface facing away from the combustion space, bears a sealing seat 8 for the control needle 2 and a further sealing seat 9 for the sleeve 3.The sleeve 3 is surrounded by an annular storage space 10 for the purpose of supplying fuel, the said space having an inlet passage 11 which is connected to a high-pressure fuel supply (not shown).

The control needle 2 has a collar 12 which supports a spring element 13 that presses the sleeve 3 onto its sealing seat 9.

At the combustion-space end, the control needle 2 has a frustoconical end 14 by means of which it rests on the sealing seat 8 in the closed condition. The sealing seat 9 for the sleeve 3 is arranged coaxially to the outside and directly adjacent thereto.

Starting from its sealing surface 15 facing this sealing seat 9, the sleeve 3 has a plurality of jetforming passages 16 in the form of virtually U-shaped recesses which are connected on the inlet side to the storage space 10 and are closed on the outlet side by a cylindrical outer surface 17 of the control needle 2 when the said needle 2 is lowered.

The passages 16 and their position will be described in greater detail with reference to the right-hand half of Fig. 2. An inlet cross-section 18, facing the storage space 10, of a passage 16 is shown rotated out of the plane of the drawing. The control needle 2 is shown in chain-dotted lines in the open position, having been displaced by its needle stroke 19. Fuel is forced out of the storage space 10 through the passages 16 and fed to the combustion space in the form of individual jets 20. Jets 21 delimiting the individual jets 20 have been drawn in as imaginary extensions of the passages 16.

There is a passage 16 arranged in each plane El, E2, E3, E4 these passages pointing past the central longitudinal axis M at a short distance from the latter. By virtue of the sloping arrangement of the passages, the angle 22 between the perpendicular projection of this central longitudinal axis M onto the respective plane El to E4 and the imaginary extension of each passage 16 is larger than the needle-seat angle 23 and the sleeve-seat angle 24.

Given an imaginary rotation of the passages 16 about the central longitudinal axis M, the individual jets 20 describe a one-sheet hyperboloid of revolution 25, the imaginary minor axis N of which lies on the central longitudinal axis M and the major axis H of which lies at a distance from the outlet opening 5 towards the combustion space.

The bead 6 is here formed completely in the annular part of the imaginary hyperboloid of revolution 25. The sealing seat 9 of the sleeve 3 is arranged on the hyperboloid shell, which runs virtually in a straight line in this region, while the sealing seat 8 is arranged in such a way that it bends away inwards in relation to this shell. This arrangement ensures that, after their emergence from the passages 16 with the control needle 2 correspondingly raised, the individual jets 20 pass freely and without hindrance thought the outlet opening 5 into the combustion space without colliding with the said opening 5 or a tapered surface 26, said surface facing the combustion space, of the bead 6.

Unwanted subsequent opening of the injection nozzle, caused by pressure oscillations, due to renewed lifting of the control needle 2 can be prevented in a simple manner in this inward-opening type than in the outward-opening nozzle type by means of known and customary measures on the injection system, e.g. a relief volume.

Claims

1. An injection nozzle for use in a reciprocating-piston internal combustion engine, which comprises a control needle which can be moved axially in a nozzle body along a central longitudinal axis, and a sleeve coaxially surrounding the said needle, both the control needle and the sleeve each forming a sealing seat with the nozzle body in the region of an injection-nozzle mouth with an annular storage space formed between the nozzle body and the sleeve, for the purpose of supplying fuel, which after the control needle has risen from its sealing seat, is sprayed by a plurality of individual jets towards a combustion space, an outlet opening at the combustion-space end of the nozzle body being surrounded by a bead which is rotationally symmetrical with respect to the central longitudinal axis and on the inner surface of which bead, which inner surface faces away from the combustion space, adjoining the outlet opening, the sealing seat of the inward-opening control needle is arranged, the sealing seat of the stationary sleeve being arranged coaxially with and directly adjacent to the sealing seat of the control needle, said sleeve being provided, adjacent to the bead, with jet-forming passages for fuel, which passages are opened when the control needle has risen from the sealing seat.

2. An injection nozzle as claimed in claim 1, in which each passage is arranged so as to point past the central longitudinal axis at a short distance from the latter in a plane, in which the angle between the imaginary perpendicular projection of the central longitudinal axis and the imaginary extension of the passage is larger than the needle-seat angle and the sleeve-seat angle.

3. An injection nozzle as claimed in claim 2, in which, given an imaginary rotation of the passages about the central longitudinal axis, the emerging individual jets describe a one-sheet hyperboloid of revolution, the imaginary minor axis of which runs along the central longitudinal axis and the major axis of which runs at a distance from the outlet opening towards the combustion space.

4. An injection nozzle as claimed in claim 3, in which the bead is formed completely in an annular part of the imaginary hyperboloid of revolution and the sealing seat of the sleeve is arranged on the hyperboloid shell, which runs virtually in a straight line in this region.

5. An injection nozzle as claimed in one or more of the preceding claims, in which the passages are designed as virtually U-shaped recesses which start from the sealing surface of the sleeve, said sealing surface facing the sleeve sealing seat, the open ends of which passages are closed by the sealing seat.

6. An injection nozzle as claimed in one or more of preceding claims 1 to 4, in which the passages are designed in such a way that they are surrounded on all sides by the sleeve.

7. An injection nozzle as claimed in claim 5 and claim 6, in which the passages in the form of U-shaped recesses are opened first, by a preliminary stroke of the control needle, and the passages surrounded on all sides by the sleeve are then opened.

8. An injection nozzle as claimed in one or more of the preceding claims, in which the sleeve is spring-biased against the sealing seat, by a spring element which is supported against a collar of the control needle.

9. An injection nozzle as claimed in one or more of the preceding claims, in which the sleeve and the nozzle body are of one-piece design.

10. An injection nozzle for use in a reciprocating-piston internal combustion engine constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.