EP2765303B1 - Valve for injecting fuel - Google Patents

Description

State of the art

Valves for injecting fuel are known from the prior art in various configurations. Multi-port nozzles are often used in high-pressure injection valves, in which the fuel is injected through injection holes in a combustion chamber. In this case, it is known to provide the injection holes at an exit-side end with a so-called preliminary hole, which terminates flush with a component surface. Here, a diameter of the pilot hole is larger than a diameter of the injection holes. Furthermore, from the DE 199 37 961 A1 a fuel injection valve is known in which a two-stage gradation is provided. It has now been found that where liquid fuel wets the combustion chamber walls of the engine, undesirable pollutant emissions, in particular soot particles and unburned hydrocarbon emissions, arise. In order to avoid this formation of pollutants, the injected fuel jet must have the lowest possible jet penetration depth. A known way to achieve this is to reduce the spray hole length as far as possible (spray hole length <0.3 mm). For reasons of structural mechanical strength, however, this possibility is limited. From the JP2010248919 is another injection valve with a stepped spray hole known.

Disclosure of the invention

The valve according to the invention for injecting fuel with the features of claim 1 has the advantage that even without reducing the spray hole length atomization in the finest drops and a reduced jet penetration depth can be achieved. As a result, improved emissions are achieved. This is achieved according to the invention in that an injection hole has a cross-section which enlarges from an inlet side to an outlet side. The cross section increases stepwise in the flow direction with exactly one first and one second step. Here, the injection hole according to the invention comprises a total of three areas, namely an inlet area, an outlet area and an intermediate area, which is arranged between the inlet area and the outlet area. The three areas are each cylindrical and a length of the intermediate area in the axial direction of the injection hole is in each case shorter than a length of the inlet area and a length of the outlet area in the axial direction of the injection hole. As a result of this inventive dimensioning of the intermediate region, an aerodynamic interaction takes place between the injection jet and the air in and at the region of the injection hole. This creates a stable, local vacuum area, whereby the injected fuel jet is fanned out very well and atomization is supported in fine droplets.

The dependent claims show preferred developments of the invention.

According to the invention, a length of the intermediate portion in the axial direction of the injection hole is in a range of 1/3 to 1/2 of a length of the discharge portion in the axial direction. By adhering to this dimension of the intermediate region, a particularly good atomization and a reduced jet penetration depth were surprisingly obtained.

• wobei D1 ein Durchmesser des Eintrittsbereichs des Spritzlochs ist,
• D2 ein Durchmesser des Zwischenbereichs des Spritzlochs ist, L1 eine Länge des Eintrittsbereichs in Axialrichtung ist und
• L3 eine Länge des Austrittsbereichs in Axialrichtung ist.

More preferably, a diameter of the intermediate region satisfies the following inequality: $$\frac{D1}{2}+\tan \left(20°\right)\times \left(600\mu m-L1-L3\right)+20\mu m\le \mathrm{<figure-callout\; id="2"\; label="D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">D</figure-callout>}2\le \frac{D1}{2}+\tan \left(20°\right)\times \left(600\mu m-L1-L3\right)+75\mu m$$

• where D1 is a diameter of the entrance area of the injection hole,
• D2 is a diameter of the intermediate portion of the injection hole, L1 is a length of the entry portion in the axial direction, and
• L3 is a length of the exit region in the axial direction.

More preferably, a length L2 of the intermediate region is in a range of 40 μm to 80 μm, preferably 50 μm to 70 μm. More preferably, a diameter D1 of the inlet region in a range of 100 microns to 250 microns, preferably 120 microns to 230 microns. Furthermore, a diameter D3 of the exit region is preferably in a range from 400 μm to 600 μm, preferably 420 microns to 580 microns and is more preferably about 470 microns. More preferably, a diameter D2 of the intermediate region in a range of 250 microns to 450 microns, preferably 280 microns to 420 microns.

More preferably, the valve comprises a number of 5 to 10 spray holes. The spray holes are particularly preferably all constructed identically.

According to a further preferred embodiment of the invention, the valve comprises a spray perforated disk, in which the injection holes are arranged.

Preferably, a length L1 of the entry region is greater than a length L3 of the exit region. More preferably, a length L1 of the inlet region is greater than one half of a total length L of the injection hole. Preferably, the total length L of the injection hole is greater than 0.3 mm.

According to a further preferred embodiment of the invention, the inlet region, the intermediate region and the outlet region are arranged concentrically to the center axis of the injection hole.

The valve according to the invention is preferably used for high-pressure direct injection.

Brief description of the drawings

Figur 1

eine schematische Schnittansicht eines Ventils gemäß einem bevorzugten Ausführungsbeispiel der Erfindung und

Figur 2

eine schematische, vergrößerte Darstellung eines Spritzlochs des erfindungsgemäßen Ventils.

Hereinafter, a preferred embodiment of the invention will be described in detail with reference to the accompanying drawings. In the drawing is:

FIG. 1

a schematic sectional view of a valve according to a preferred embodiment of the invention and

FIG. 2

a schematic, enlarged view of a spray hole of the valve according to the invention.

Embodiments of the invention

The following is with reference to the FIGS. 1 and 2 a valve 1 according to a preferred embodiment of the invention described in detail.

How out FIG. 1 As can be seen, the fuel injection valve 1 comprises a plurality of spray holes 2 arranged at an injection-side end of the valve 1. The valve 1 further comprises a valve housing 10, a magnet armature 11 which is connected to a valve needle 17 and 12 has passage openings, and a magnetic coil 13. The valve 1 further comprises a closing spring 14 and an electrical connection 15. A valve seat 6 is at a Valve body 16 is provided.

The magnet armature 11 is movable in the axial direction YY of the valve 1 and releases the spray holes 2 or closes them. FIG. 1 shows the closed state of the valve. 1

An injection hole 2 according to the invention is shown in detail in FIG FIG. 2 shown. In this embodiment, all the injection ports of the valve are constructed the same, but it is also possible that the injection holes 2 are constructed differently.

How out FIG. 2 it can be seen, the injection hole 2 comprises exactly one inlet region 21, an intermediate region 22 and an outlet region 23. The intermediate region 22 is arranged in the flow direction A between the inlet region 21 and the outlet region 23.

The armature, which in FIG. 2 is not shown, it closes the injection hole 2 at an inlet side 3 and gives the inlet side 3 free. When the spray hole 2 is released, the fuel to be injected enters the spray hole at the inlet side 3 and flows through the spray hole 2 in the flow direction A. The fuel then exits again at an outlet side 4 of the spray hole 2. This results in a fanning out of the fuel to be injected into a fuel spray.

According to the invention, only the three regions, namely the inlet region 21, the intermediate region 22 and the outlet region 23, are provided. Here, the inlet region 21 has a first diameter D1 which is smaller than a second diameter D2 of the intermediate region 22 and a third diameter D3 of the outlet region 23.

Further, the entrance portion 21 has a length L1 in the axial direction X-X of the injection hole 2, which is larger than a length L2 of the intermediate portion 22 and a length L3 of the exit portion 23. Here, the length L2 of the intermediate portion is the shortest. L designates the total length of the injection hole in the axial direction X-X.

The inlet region 21, the intermediate region 22 and the outlet region 23 are each provided cylindrically and concentric with the central axis X-X of the spray hole 2.

The construction of the spray hole 2 with exactly three areas thus results in a first paragraph 24 and a second paragraph 25. By the invention defined dimensions of the stepped spray hole 2 thus a spray can be generated, due to the geometric dimensions of the intermediate portion 22 due to aerodynamic interactions between the fuel injection jet and the air creates a stable, local low pressure area. This results in a fanning of the exiting fuel jet and improved atomization in the finest droplets. Furthermore, it is possible to increase the total length of the spray hole 2 compared to the previous spray holes without disadvantages in the mixture preparation by the short formation of the intermediate region 22 in the axial direction. Furthermore, the design of the intermediate region 22 according to the invention also results in the reduction of the jet penetration depth described in the prior art.

The two-stage graduated injection hole 2 according to the invention is preferably produced by machining or else by, for example, metal injection molding (MIM) or by laser drilling or by erosion. In this way, in particular a high accuracy of the dimensions of the diameter and the lengths of the three regions in the axial direction X-X of the injection hole can be ensured.

Claims (9)

1. Valve for injecting fuel, comprising

   - at least one spray hole (2) which has a cross section which increases in a throughflow direction (A) from an inlet side (3) to an outlet side (4),

   - wherein the enlargement of the spray hole (2) takes place in stepped fashion in the throughflow direction by way of a first step (24) and a second step (25),

   - wherein the spray hole (2) comprises a total of three regions: an inlet region (21), an outlet region (23) and an intermediate region (22), wherein the intermediate region (22) is arranged between the inlet region (21) and the outlet region (23) in the throughflow direction (A),

   - wherein the inlet region (21), the outlet region (23) and the intermediate region (22) are each of cylindrical form, and

   - wherein a length (L2) of the intermediate region (22) in an axial direction (X-X) of the spray hole (2) is shorter than a length (L1) of the inlet region (21) in the axial direction (X-X) and shorter than a length (L3) of the outlet region (23) in the axial direction (X-X),

   characterized
   in that a length (L2) of the intermediate region (22) in the axial direction (X-X) of the spray hole (2) amounts to one third to one half of a length (L3) of the outlet region (23).
2. Valve according to Claim 1, characterized in that a diameter (D2) of the intermediate region (22) satisfies the following inequation: $$\frac{D1}{2}+\tan \left(20°\right)\times \left(600\mu m-L1-L3\right)+20\mu m\le D2\le \frac{D1}{2}+\tan \left(20°\right)\times \left(600\mu m-L1-L3\right)+75\mu m$$

   

   wherein D1 is a diameter of the inlet region (21),

   - L1 is a length of the inlet region (21), and

   - L3 is a length of the outlet region (23).
3. Valve according to one of the preceding claims, characterized in that a length (L2) of the intermediate region (22) lies in a range from 40 µm to 80 µm.
4. Valve according to one of the preceding claims, characterized in that a diameter (D1) of the inlet region (21) lies in a range from 100 µm to 250 µm, and/or a diameter (D3) of the outlet region (23) lies in a range from 400 µm to 600 µm, and/or a diameter (D2) of the intermediate region (22) lies in a range from 250 µm to 450 µm.
5. Valve according to one of the preceding claims, comprising a number of 5 to 10 spray holes (2).
6. Valve according to one of the preceding claims, characterized in that the spray hole (2) is provided in a spray hole disc.
7. Valve according to one of the preceding claims, characterized in that the length (L1) of the inlet region (21) is greater than the length (L3) of the outlet region (23).
8. Valve according to one of the preceding claims, characterized in that the length (L1) of the inlet region (21) is greater than half of a total length (L) of the spray hole (2) in the axial direction (X-X) and/or in that the total length (L) of the spray hole (2) is greater than 0.3 mm.
9. Valve according to one of the preceding claims, characterized in that the inlet region (21), the intermediate region (22) and the outlet region (23) are concentric with respect to the central axis (X-X) of the spray hole (2).

Images