Fuel injection nozzle

Abstract

The invention relates to a fuel injection nozzle for use in an internal combustion engine, having a nozzle body (1), in which is formed a pressure chamber (2) fillable with fuel under high pressure and in which a longitudinally displaceable nozzle needle (4) is arranged, wherein the nozzle needle (4) has a sealing face (5) with which it interacts with a conical body seat (7) formed in the nozzle body (1) and thereby opens and closes the connection from the pressure chamber (2) to a blind hole (10). The blind hole (10) forms a cylindrical section (12) directly adjoining the body seat (7) so that an inlet edge (11) is formed at the transition between the body seat (7) and the blind hole (10). In the nozzle body (1) is formed at least one injection opening (14) which opens into the blind hole (10). The cylindrical section of the blind hole (10) has a reduced diameter so that a shoulder (16) is formed in the blind hole (10), wherein the at least one injection opening (14) opens into the blind hole (10) between the shoulder (16) and the inlet edge (11).

Claims

1. A fuel injection nozzle for use in an internal combustion engine, the fuel injection nozzle having a nozzle body (1), in which is formed a pressure chamber (2) Tillable with fuel under high pressure and in which a longitudinally movable nozzle needle (4) is arranged, wherein the nozzle needle (4) has a sealing surface (5), by means of which the nozzle needle interacts with a conical body seat (7) formed in the nozzle body (1) and thereby opens and closes a connection from the pressure chamber (2) to a blind hole (10), wherein the blind hole (10) forms a cylindrical section (12) directly adjoining the body seat (7), such that an inlet edge (11) is formed at a transition between the body seat (7) and the blind hole (10), and the fuel injection nozzle having at least one injection opening (14), which is formed in the nozzle body (1) and opens into the blind hole (10), characterized in that the cylindrical section of the blind hole (10) makes a transition to a reduced diameter at an end of the cylindrical section remote from the inlet edge (11), such that a shoulder (16) is formed at the transition, wherein the at least one injection opening (14) opens into the blind hole (10) between the shoulder (16) and the inlet edge (11), wherein a substantially hemispherical blind hole base (13) directly adjoins the shoulder (16) at an end of the blind hole (10) remote from the body seat (7).

2. The fuel injection nozzle as claimed in claim 1, characterized in that the shoulder (16) is in the form of an annular disk.

3. The fuel injection nozzle as claimed in claim 1, characterized in that the shoulder (16) is conical.

4. The fuel injection nozzle as claimed in claim 1, characterized in that a transition from the cylindrical section (12) of the blind hole to the shoulder (16) or from the shoulder (16) to the adjoining blind hole base (13) is rounded.

5. The fuel injection nozzle as claimed in claim 1, characterized in that the shoulder (16) has a constant depth (T) over an entire circumference of the blind hole (10).

6. The fuel injection nozzle as claimed in claim 5, characterized in that the depth (T) of the shoulder (16) is 5 μm to 100 μm.

7. The fuel injection nozzle as claimed in claim 1, characterized in that a plurality of injection openings (14) is formed in the nozzle body (1), wherein the injection openings open into the blind hole (10) between the shoulder (16) and the inlet edge (11).

8. The fuel injection nozzle as claimed in claim 1, characterized in that at least one injection opening (15) opens into the conical body seat (7).

9. The fuel injection nozzle as claimed in claim 1, characterized in that a plurality of injection openings (14) is formed in the nozzle body (1), wherein the injection openings open into the blind hole (10) between the shoulder (16) and the inlet edge (11), and wherein the injection openings (14) are distributed uniformly over a circumference of the nozzle body (1).

10. The fuel injection nozzle as claimed in claim 1, wherein the nozzle needle (4) moves in a closing direction towards a closed position in which the nozzle needle (4) is in contact with the conical body seat (7), and wherein a furthest injection opening in the closing direction is between the shoulder (16) and the inlet edge (11).

11. The fuel injection nozzle as claimed in claim 1, wherein the nozzle needle (4) seats on the conical body seat (7), and wherein the only portion of the nozzle body (1) that contacts the nozzle needle (4) is the conical body seat (7).

12. A fuel injection nozzle for use in an internal combustion engine, the fuel injection nozzle having a nozzle body (1), in which is formed a pressure chamber (2) Tillable with fuel under high pressure and in which a longitudinally movable nozzle needle (4) is arranged, wherein the nozzle needle (4) has a sealing surface (5), by means of which the nozzle needle interacts with a conical body seat (7) formed in the nozzle body (1) and thereby opens and closes a connection from the pressure chamber (2) to a blind hole (10), wherein the blind hole (10) forms a cylindrical section (12) directly adjoining the body seat (7), such that an inlet edge (11) is formed at a transition between the body seat (7) and the blind hole (10), and the fuel injection nozzle having at least one injection opening (14), which is formed in the nozzle body (1) and opens into the blind hole (10), characterized in that the cylindrical section of the blind hole (10) makes a transition to a reduced diameter at an end of the cylindrical section remote from the inlet edge (11), such that a shoulder (16) is formed at the transition, wherein the at least one injection opening (14) opens into the blind hole (10) between the shoulder (16) and the inlet edge (11), wherein the nozzle needle (4) moves in a closing direction towards a closed position in which the nozzle needle (4) is in contact with the conical body seat (7), and wherein a furthest injection opening in the closing direction is between the shoulder (16) and the inlet edge (11).

13. A fuel injection nozzle for use in an internal combustion engine, the fuel injection nozzle having a nozzle body (1), in which is formed a pressure chamber (2) Tillable with fuel under high pressure and in which a longitudinally movable nozzle needle (4) is arranged, wherein the nozzle needle (4) has a sealing surface (5), by means of which the nozzle needle interacts with a conical body seat (7) formed in the nozzle body (1) and thereby opens and closes a connection from the pressure chamber (2) to a blind hole (10), wherein the blind hole (10) forms a cylindrical section (12) directly adjoining the body seat (7), such that an inlet edge (11) is formed at a transition between the body seat (7) and the blind hole (10), and the fuel injection nozzle having at least one injection opening (14), which is formed in the nozzle body (1) and opens into the blind hole (10), characterized in that the cylindrical section of the blind hole (10) makes a transition to a reduced diameter at an end of the cylindrical section remote from the inlet edge (11), such that a shoulder (16) is formed at the transition, wherein the at least one injection opening (14) opens into the blind hole (10) between the shoulder (16) and the inlet edge (11), wherein the nozzle needle (4) seats on the conical body seat (7), and wherein the only portion of the nozzle body (1) that contacts the nozzle needle (4) is the conical body seat (7).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Various illustrative embodiments of the fuel injection nozzle according to the invention are shown in the drawing, in which:

(2) FIG. 1 shows a longitudinal section through a fuel injection nozzle of the kind known from the prior art,

(3) FIG. 2 shows a first illustrative embodiment of a fuel injection nozzle according to the invention,

(4) FIG. 3 shows another illustration of the fuel injection nozzle according to FIG. 2,

(5) FIG. 4 shows the same fuel injection nozzle as in FIG. 3, wherein the profile of the fuel flow within the blind hole is illustrated, and

(6) FIG. 5 and FIG. 6 show further illustrative embodiments of the fuel injection nozzle according to the invention with modified shoulders within the blind hole.

DETAILED DESCRIPTION

(7) FIG. 1 illustrates a fuel injection nozzle according to the prior art in longitudinal section, wherein only the essential parts of the fuel injection nozzle are shown. The fuel injection nozzle has a nozzle body 1, in which a pressure chamber 2 that can be filled with fuel under high pressure is formed. Here, the compressed fuel is made available in a “common rail”, for example, a high-pressure fuel reservoir which is fed by a high-pressure fuel pump, for example. Arranged in a longitudinally movable manner in the pressure chamber 2 is a plunger-shaped nozzle needle 4, which has, at its combustion chamber end, a sealing surface 5 which is of conical design and by means of which the nozzle needle 4 interacts with a likewise conical body seat 7 in order to open and close a flow cross section. Adjoining the conical body seat 7 is a blind hole 10, which has a cylindrical section 12 and a blind hole base 13, wherein the blind hole base 13 is of substantially hemispherical design. An injection opening 14 starts from the blind hole 10, wherein it is also possible to provide a plurality of injection openings, through which the fuel can emerge and enter the combustion chamber of an internal combustion engine. When the nozzle needle 4 is resting by means of the sealing surface 5 on the body seat 7, the flow cross section between the nozzle needle 4 and the body seat 7 is closed, with the result that the fuel available in the pressure chamber 2 remains therein under high pressure; the blind hole 10 is thus unpressurized and, accordingly, no fuel emerges via the injection openings 14.

(8) If an injection is to take place, the nozzle needle 4 is moved in the longitudinal direction by a suitable mechanism, with the result that it rises from the body seat 7 and exposes a flow cross section between the sealing surface 5 and the body seat 7, as a result of which fuel flows under high pressure out of the pressure chamber 2 into the blind hole 10. From there, the fuel flows onward through one or more injection openings 14 and thus enters the combustion chamber. As it emerges from the injection openings 14, the fuel is atomized, i.e. the jet breaks up and forms a large number of small fuel droplets, which mix well with the oxygen in the combustion chamber and thus form a combustible mixture. To end injection, the nozzle needle 4 is pushed back into its closed position in contact with the body seat 7, thus ending the inflow of fuel into the blind hole 10.

(9) FIG. 2 shows a first illustrative embodiment of a fuel injection nozzle according to the invention, which differs from the fuel injection nozzle shown in FIG. 1 in having a shoulder 16 within the blind hole 10. The right-hand side of this fuel injection nozzle is illustrated again on an enlarged scale in FIG. 3. The blind hole 10 has a cylindrical section 12, which directly adjoins the body seat 7. The cylindrical section 12 is delimited by a shoulder 16, which is caused by a diameter reduction with a depth T, wherein the shoulder 16 in this illustrative embodiment is of conical design. The depth T is 5 to 100 μm (0.005 to 0.1 mm), with the result that the blind hole 10 has only a slightly larger volume than the known variant embodiment shown in FIG. 1. This is advantageous because a large blind hole volume can lead to unintended emergence of fuel via the injection openings 14, even during the injection pauses, this fuel then emerging without pressure and therefore with inadequate atomization into the combustion chamber and potentially leading there to increased hydrocarbon emissions. The injection openings 14 always open into the cylindrical section 12 of the blind hole 10, i.e. between the shoulder 16 and the inlet edge 11. This ensures uniform distribution of the fuel between all the injection openings 14 since all the injection openings 14 have the same inlet characteristic.

(10) The effect of the shoulder 16 is illustrated in FIG. 4, where the same fuel injection nozzle as that in FIG. 3 is illustrated once again. In the open position of the nozzle needle 4, the fuel flows between the sealing surface 5 and the body seat 7 into the blind hole 10. Since the nozzle needle 4 is at a relatively large distance from the body seat 7 at a late time in the opening stroke movement, the fuel flows into the blind hole 10 without major turbulence, following the sealing surface 5, and thus enters the blind hole base 13 without major turbulence. From there, the fuel flows back at the side and, in the process, flows over the shoulder 16. This flow over the shoulder 16 leads to swirling of the fuel before it enters the injection hole 14, this being continued via the injection hole 14 and, finally, as the fuel emerges from the injection hole 14, leading to improved atomization.

(11) FIG. 5 shows another illustrative embodiment of the fuel injection nozzle according to the invention. This differs from the fuel injection nozzle shown in FIG. 3 and FIG. 4 in having a rounded transition between the cylindrical section of the blind hole 12 and the shoulder 16 and/or from the shoulder 16 to the blind hole base 13. The rounding makes it possible to minimize notch stresses of the kind which would occur with a sharp-edged profile, but the effect in respect of the turbulence introduced is less. In the case of the illustrative embodiment shown in FIG. 6, in contrast, the shoulder 16 is designed as an annular disk, that is to say it has a right-angled transition between the cylindrical section 12 of the blind hole 10 and the shoulder 16. On the one hand, this promotes the introduction of turbulence but, on the other hand, notch stresses that may impair the strength of the nozzle body occur at the sharp-edged transition, especially at very high injection pressures.

(12) In FIG. 2, in addition to the injection openings 14, of which it is also possible for a plurality to be arranged in a manner distributed over the circumference of the nozzle body 1, a further injection opening 15 starting directly from the body seat 7 is formed. Such injection openings 15 are a characteristic of “seat hole nozzles” and have a different jet characteristic from the injection openings 14 which start from the blind hole 10. Particularly in the case of combustion chambers which are large, it is possible in this way to distribute the fuel effectively over the entire combustion chamber volume.