WO2015052031A1 - Nozzle element for an injection valve, and injection valve - Google Patents

Abstract

The invention relates to a nozzle element (12) for an injection valve, having a nozzle element recess (14) with at least one injection opening (24). The nozzle element recess (14) can be hydraulically coupled to a high-pressure circuit of a fluid. Furthermore, with respect to a central longitudinal axis (LA), the at least one injection opening (24) has a first region (B1) with a constant cross-section, said first region adjoining the nozzle element recess (14), and a second region (B2) with a substantially divergent cross-section.

Description

description

The invention relates to a nozzle body for an injection valve, which has a nozzle body recess. Furthermore, the invention relates to an injection valve.

Due to increasingly stringent statutory provisions regarding the permissible pollutant emissions of internal combustion engines, which are arranged in motor vehicles, it is necessary to take various measures by means of which the

Pollutant emissions are lowered. A possible starting point here is to reduce the pollutant emissions generated by the internal combustion engine. Here, the formation of soot is highly dependent on the preparation of the air / fuel mixture in the respective cylinder of the internal combustion engine.

A correspondingly improved mixture preparation can be achieved if the fuel is metered under very high pressure. In the case of diesel internal combustion engines, the fuel pressures are up to over 2000 bar. Such high pressures make both high demands on the material of the nozzle body as well as their construction. At the same time larger forces must be taken from the nozzle body or the nozzle assembly ^¬ .

Currently, injectors with multiple injection holes are the most widely used on the market. In order to ensure the lowest possible penetration (penetration) of the injection jet and the largest possible opening angle of the beam cone in a cylinder of an internal combustion engine. ^

An object of the invention is to provide a nozzle body or an injection valve, which allow a reliable and precise operation. According to a first aspect of the invention, a nozzle body for an injection valve is described which has a nozzle body recess with at least one injection opening. In this case, the nozzle body recess can be hydraulically coupled to a high pressure circuit of a fluid. Furthermore, the at least one injection opening has, with respect to a central longitudinal axis, a first region with a constant cross section adjoining the nozzle body recess and a second region with a substantially diverging cross section.

The nozzle body according to the first aspect of the invention provides that said at least one injection opening two cross-section ^¬ areas, wherein the first region is characterized by a constant cross-section and the second region by a diverging cross-section. This has the advantage that a sufficiently large beam angle and a low penetration of the fluid jet can be achieved. On the other hand, accumulations of liquid and / or droplet-shaped fluid residues, coking and thus deposits are avoided, above all, by the provision of a diverging cross section in the second region of the injection opening. In particular, the accumulation of fluid residues, for example fuel, in contrast to corner areas in a stepped bore can be substantially prevented. The advantages of the invention are based on the recognition that the second region of the injection opening causes by its diverging cross-section a self-cleaning effect, so possibly wetted with fluid surfaces of the second portion of the injection opening and / or adhering to this Combustion residues due to the high speeds of the fluid are ^¬ Strömungsgeschwin in subsequent injection operations purified by gas entrainment or washed away. The fluid residues are sheared due to high shear forces resulting from backflow from the surfaces of the second region, taken away by the fluid flow and fed back into the combustion chamber. In this way a permanent wetting of the surfaces of the injection opening and thus the formation of coked material is prevented.

In contrast, would he have in injection valves with a stepped bore with constant cross section as disadvantageous ^¬ that are and mainly during the injection phase by back-flow of the fluid surfaces of the stepped bore through the fluid, for example force or fuel, be ^¬ wets thereby residues, especially in the corner areas of the stepped bore. This leads to deposits that consist essentially of carbon and arise at high temperatures by coking these fluid residues on the stepped bores. As a rule, these deposits have a porous structure, which further promotes the coking process by absorption of the gaseous and / or liquid fluid during subsequent injection processes. This leads to increased hydrocarbon (also HC) and particulate emissions.

According to an advantageous embodiment of the cross section of the second portion of the at least one injection opening ^¬ diverges conically. Thus, a directed flow within the injection hole is produced in particular that favors in particular ^¬ sondere shearing of fluid, such as fuel and / or deposits of the surfaces. According to a further advantageous embodiment, the second region of the at least one injection opening has a step-shaped cross-sectional widening. By providing a step-shaped cross-sectional widening, in particular a sufficiently large opening angle of the jet cone and a low penetration (penetration) of the injection jet into a cylinder of an internal combustion engine can be achieved.

According to a further advantageous embodiment, the step-shaped cross-sectional widening along an inner edge has a rounding. By providing a curve along an inner edge of the step-shaped cross-sectional widening, substantially unfavorable vortices and thus fluid residues in the corner regions of the second region of the injection opening are avoided.

According to a further advantageous embodiment, the at least one injection opening has a rounding along at least one outer edge. This further improves the self-cleaning effect of the injection opening.

According to a second aspect of the invention, an injection valve with a nozzle body according to the first aspect of the invention is described. The injection valve has substantially the aforementioned advantages.

Further advantageous embodiments are disclosed in the following detailed description of exemplary embodiments and the dependent claims.

Embodiments of the invention are described below with reference to the attached figures. In the figures, similar components of different embodiments are provided with the same reference numerals. In the figures show:

Figure 1 is a schematic sectional view of an injection ^¬ valve having a nozzle body,

FIG. 2 shows an injection opening with a stepped bore,

FIG. 3 shows an injection opening according to a first exemplary embodiment,

Figure 4 is an injection port according to a second embodiment and

FIG. 5 shows an injection opening according to a third exemplary embodiment.

FIG. 1 shows an injection valve with a nozzle assembly 10 and an actuator 11. The actuator 11 interacts functionally with the nozzle assembly 10.

The nozzle assembly 10 has a nozzle body 12 and the actuator 11 has an injector body 13. The nozzle body 12 is fixedly coupled to the injector body 13 by means of a nozzle retaining nut 30. The nozzle body 12 and the injector body 13 form a common housing of the injection valve.

The nozzle body 12 has a nozzle body recess 14 with a central axis Z and a wall 16. In the nozzle body recess 14, a nozzle needle 18 is arranged, which forms the nozzle assembly 10 together with the nozzle body 12. The nozzle needle 18 has at one end a needle tip 20. The nozzle needle 18 is guided in a region of the nozzle body recess 14 and biased by a nozzle spring 22. In the nozzle body 12, injection openings 24 are preferably arranged near the needle tip 20. In the Einspritzöff ^¬ voltages 24 surrounding region of the nozzle body 12 may consist of a sintered metal. In the nozzle body 12, preferably a plurality of injection openings 24 are formed, which can form an injection hole circle.

The injector body 13 has a recess in which an actuator 40 is arranged. The actuator 40 is designed as a stroke steep drive. The actuator 40 acts on the

Nozzle needle 18, so that they can perform a movement in the direction of the central axis Z.

The nozzle spring 22 exerts on the nozzle needle 18 a force acting in the closing direction, so that it prevents a flow of a fluid through the plurality of injection openings 24 arranged in the nozzle body 12, when no further forces act on the nozzle needle 18. Upon actuation of the actuator 40, the nozzle needle 18 is moved in the axial direction from its closed position to its open position, in which it releases the fluid flow through the injection openings 24.

The term "fluid" may include a fuel, such as a diesel or gasoline fuel, but the term may include other substances, such as organic compounds such as urea.

In the following Figures 2 to 5 each show an enlarged view of a section II of Figure 1, which shows in detail the structural design of an injection port 24 each.

FIG. 2 shows an enlarged, schematic sectional view of an injection opening 24 with a stepped bore SB. Is the Fluid flow through the nozzle needle 18 (Figure 1) released so enters the fluid according to the flow direction SR under high pressure in the injection port 24 a. In this case, a beam cone angle is formed in the region of the stepped bore SB. The fluid, for example fuel flows finely atomized and / or gas in the combustion chamber and the cylinder of an internal combustion engine (not shown), where it mixes with air sucked in by the internal combustion engine air and a homo ^¬ genisierung of the air / fluid substantially Mixture is achieved. This results in backflow RS of the fluid in the region of the stepped bore SB. The back-flowed air / fluid mixture is partially entrained by gas entrainment GM from the injection jet according to the flow direction SR and redistributed in the cylinder. In this case, the flow direction of the return flow RS is substantially reversed. Due to the flow direction SR of the incoming fluid jet and the return flow RS, a stagnation region STB is formed, which has a cone angle β which is slightly larger than the beam cone angle and describes the region in which the flow directions of the fluid are reversed.

A disadvantage with an injection opening according to FIG. 2 is that the walls W of the stepped bore SB are permanently wetted by the fluid and, especially in the corner regions E of the stepped bore SB, residues of the fluid form. These residues may coke at high temperatures, such as those prevailing during the injection process of the fluid in the combustion chamber of a cylinder, resulting in carbonaceous deposits. These deposits lead to a high pollutant emission. In particular, unfavorable vortex flows favor WS in the

Corner regions E of the stepped bore SB an accumulation of fluid. Especially after several injections these lead to an increase in deposits. ₀

 O

FIG. 3 shows an enlarged, schematic sectional view of an injection opening 24 according to a first exemplary embodiment. The injection opening 24 has a first region Bl with a constant cross-section and a second region B2 with a stepped cross-sectional widening SQE. The step-shaped cross-sectional widening SQE in this case has a divergent, conical cross section with an annular step S. The two cross sections are rotationally symmetrical with respect to the in the illustrated embodiment

Longitudinal axis LA. The second region B2 has a cone angle γ. The first area Bl adjoins the nozzle body recess 14, while the second area B2 is finally arranged with the outside AS of the nozzle body 12. If a fluid from the nozzle body recess 14 enters the first region B1 of the injection opening 24 under high pressure according to the flow direction SR, a beam cone angle is formed depending on the height H and the cross section of the first region B1 when the fluid exits the first region B1 out. Due to the conical, diverging cross section of the second region B2 of the injection opening 24, a favorable return flow RS occurs in the second region B2. In particular, in the corner regions E of the second region B2 substantially no unfavorable vortex flows WS occur. This ensures that the walls W of the second region B2, which are wetted with fluid as a result of an earlier injection process, are washed away due to the high flow velocity of the fluid, in particular the ^return flow RS, and are absorbed by the incoming fluid jet , This process is also referred to as gas entrainment GM and is dependent on the dimensioning of the width B or the height H2 of the second region. As a result, a self-cleaning effect of the injection opening 24 that repeats itself with each injection process is achieved. _

 y

The first region Bl is preferably designed as a cylindrical bore which has a substantially circular cross-section. The second area B2 is, as already described be ^{¬ designed} as a stepped cross-sectional widening SQE with the step S. Preferably, the width B of the ring ^¬- shaped step S has a length of less than 100 ym, in particular 50 ym. The height H2 preferably has a length of less than 600 ym. The second region B2 preferably has a Ke ^¬ gel angle γ, which is between 14 ° and 21 °. Alternatively, it is also conceivable that the second region B2 has no step S.

In the illustrated embodiment, the injection port 24, the two areas Bl and B2, wherein the second region B2 connects to the first region Bl. Alternatively, it is conceivable that one or more further cross-sectional regions, for example a region with a constant cross section which is different from the first region B1, are arranged between the first region B1 and the second region B2. It is likewise conceivable for the second area B2 to be followed by one or more further cross-sectional areas and the second area B2 not to terminate with the outer side AS of the nozzle body 12.

In the figures 4 and 5 described below, for reasons of clarity, individual features of FIGS. 2 and 3 are no longer shown or provided with reference numerals. However, this does not explicitly exclude their existence.

FIG. 4 shows an injection opening 24 according to a second exemplary embodiment. The injection port 24 comprises We ^¬ sentlichen the same features as the embodiment according to Figure 3, except that a peripheral rounding R is provided in the corner regions E of the second area B2. Preferably, this rounding has a radius of more than 10 ym. Such a rounding favors the self-cleaning process of the walls W of the second region B2 of the injection opening 24, primarily by a substantially favorable return flow RS. In this embodiment as well, there are essentially no unfavorable vortices in the corner regions E, and a high shearing effect by the backflow RS in the region of the walls W can be achieved. In this way, be ^¬ netted walls may be better W liberated by the injection process by the gas delivery GM or the backflow RS deposits and fluid retention in comparison to the embodiment of FIG. 3 This is mainly due to the fact that there is no abrupt in the corners E

Cross-sectional transition there. FIG. 5 shows an injection opening 24 according to a third

Embodiment, which is designed substantially similar to the ^{¬ formations} according to Figures 3 and 4. In this case, the second region B2 of the injection opening 24 a plurality of curves R, so that forms a tulip or flower-shaped cross-section. The provision of several

Rounding R in the second region B2 favors the self-cleaning effect of the injection port 24 on. In particular, a substantially favorable return flow RS and an optimal gas entrainment GM of the fluid flowing back and any fluid accumulation in the second region B2 are ensured. In particular, due to the continuous cross-sectional profile in the second region B2, essentially a fluid accumulation is avoided from the outset. The injection openings 24 described with reference to FIGS. 3 to 5 have an angular or angular transition in the fluid inlet region of the first region B1, that is to say on the side of the nozzle body recess 14. Alternatively, in the entry region of the injection opening 24, an annular Step, chamfers and / or curves may be provided. Furthermore, the cross section of the first region Bl can also have elliptical or other geometrical configurations, for example the outer contour of two partially overlapping circles.

Further, the injection port 24 described with reference to the three embodiments is not limited to a specific pressure range. Rather, such an injection opening 24 can be used in an injection valve for a gasoline internal combustion engine up to a pressure range of 500 bar and / or for a diesel internal combustion engine up to 2000 bar. Ge ^¬ optionally the geometric dimensions of the injection orifice 24 must be adjusted in a manner known to the expert in the corresponding pressure range. An injection port 24 may also be provided in other injectors that are not intended for diesel or gasoline internal combustion engines. By means of the injection openings 24 described with reference to the exemplary embodiments, a very fine atomization of the fluid and a large jet angle at the outlet of the injection openings 24 can be achieved. In particular, when used in an internal combustion engine can be achieved in this way, a good distribution of the fluid in the sucked by the internal combustion engine air and a good homogenization of the fluid-air mixture in a combustion chamber of the internal combustion engine. The wetting of the surfaces of the injection openings 24 is kept very low due to the structural design or even avoided due to the described self-cleaning effect. This makes, for example, no special coating measures necessary, whereby manufacturing costs can be reduced. Also, there are no special surface treatments, such as the introduction of grooves or polishing measures, needed. In addition, a simple and production-ready production of the injection openings 24 is possible.

The invention is not limited to the specified embodiment. In particular, it is possible to combine the features rela ^¬ hung as functions of the various embodiments with each other.

Reference sign list

10 nozzle assembly

 11 actuator

 12 nozzle body

 13 Inj ector body

 14 nozzle body recess

 16 wall

 18 nozzle needle

 20 needle group

 22 nozzle spring

 24 injection opening

 30 nozzle retaining nut

 40 actuator

 Beam cone angle

ß cone angle

 Y cone angle

 AS outside

 B width

 Bl first area

 B2 second area

 E corner area

 GM gas taking

 Hl, H2 height

 LA longitudinal axis

 R rounding

 RS return flow

 S level

 SB stepped bore

 SQE step-shaped cross-sectional widening

SR flow direction

 STB stagnation area

 W wall

S vortex flow Z central axis

Claims

claims 1. nozzle body (12) for an injection valve, comprising a nozzle body recess (14) with at least one injection opening (24), wherein  - The nozzle body recess (14) is hydraulically coupled to a high pressure circuit of a fluid, and - The at least one injection port (24) with respect to a central longitudinal axis (LA) to the Düsenkörperaus ^¬ recess (14) subsequent first region (Bl) having a constant cross section and a second region (B2) having a substantially divergent cross section. 2. nozzle body (12) according to claim 1,  in which the cross section of the second region (B2) of the at least one injection opening (24) diverges conically. 3. nozzle body (12) according to any one of claims 1 or 2,  in which the second region (B2) of the at least one injection opening (24) has a stepped shape  Cross-sectional expansion (SQE) has. 4. nozzle body (12) according to claim 3,  in which the step-shaped cross-sectional widening (SQE) has a rounding (R) along an inner edge. 5. nozzle body (12) according to one of claims 1 to 4, wherein the at least one injection opening (24) along at least one outer edge has a rounding (R). 6. injection valve with a nozzle body (12) according to any one of the preceding claims.