DE102017204298A1 - injector - Google Patents

Abstract

The invention relates to an injector (1), in particular a fuel injector (1), comprising at least one first injection hole (21) with a first axis (22) and a second injection hole (31) with a second axis (32) for introducing Fuel (10), wherein at least the first and second axes (22, 32) intersect on an injector-facing side (20) of the injector (1) at an intersection (37), and wherein the injection hole (21, 31) has a rounded inlet (33), a tapered flow channel (34) and a sharp-edged outlet edge (36).

Description

State of the art

The present invention relates to an injector, in particular a fuel injector, for injecting fuel into a combustion chamber of an internal combustion engine, which allows increased fuel atomization by two colliding fuel jets.

Injectors are known from the prior art in various configurations and are usually used in an internal combustion engine in a combustion chamber for atomizing - so-called atomizing - of fuel. Such injectors are for example from the DE 10 2014 202 687 A1 are known and typically consist of a housing in which a pressure chamber is incorporated. Along a longitudinal axis of the pressure chamber, a closing element is movably arranged, which cooperates in a lateral movement with an attached in the housing closing element seat. The closing element thus opens and closes depending on its position one or more injection holes incorporated in the housing or in the closing element seat for injecting the fuel into the combustion chamber. The fuel is for this purpose in the pressure chamber at a high pressure, so that it is atomized when exiting the injection holes and entering the combustion chamber.

In order to meet the requirements in the field of internal combustion engines, increasingly higher pressures in the pressure chamber of the injector are used to improve the fuel atomization and the interaction of the fuel with the surrounding air. Due to the very high injection pressures in the pressure chamber of about 100-200 × 10 ⁵ Pa, a further increase in the pressure level to improve the atomization can only be achieved by considerable additional effort and thus uneconomical.

Disclosure of the invention

In contrast, the injector according to the invention with the features of claim 1 has the advantage that the injector improves fuel atomization and the interaction of the fuel with the surrounding air in the combustion chamber even at currently used pressures. Due to the improved fuel atomization, the size of the fuel droplets is significantly reduced, favors the mixing and the fuel with the best possible mixing and propagation in the combustion chamber, without the fuel wetting the combustion chamber walls or the spark plug. This is inventively achieved in that the injector has at least a first injection hole with a first axis and a second injection hole with a second axis for introducing fuel, wherein at least the first and the second axis intersect on an injector side facing away from the injector in an intersection , At least one of the injection holes has a rounded inlet, a tapered flow channel and a sharp-edged outlet edge, whereby the at least two formed beams are stabilized and reliably and completely collide in at least one point of intersection and thus sputter each other. In order to completely and reliably atomize the fuel jets in the collision even under highly turbulent conditions, the flow channel is designed to be convergent, ie continuously tapering in the flow direction, whereby the pressure level at the inlet of the injection hole is increased, thereby reducing cavitation or turbulence. As a result, an increased hole filling and a homogeneous flow profile is created in the flow channel, which can create a particularly stable fuel jet, which is insensitive to fluctuations and thus ensures a complete collision of the at least two intersecting fuel jets. This configuration and alignment of the injection holes allows improved atomization of the fuel even at low manufacturing tolerances, so that lower injection pressures can also be used compared to conventional injectors. This results in significant cost advantages, since on the one hand the tolerances can be made more generous and on the other hand, the strength and the choice of materials have consistent or even lower requirements.

The dependent claims show preferred developments of the invention.

Preferably, the first and second injection hole each have the same cross section. More preferably, all the injection holes have the same cross section and each fuel jet collides with at least one other fuel jet.

Preferably, the inlet of the injection holes is provided with a rounding. The inlet can be provided as a rounding with a constant radius or be designed as an optimized funnel geometry or trumpet or bell-shaped free-form surface. Through the inlet in particular the pressed from the pressure chamber into the injection holes fuel is accelerated low pressure loss, so that forms a homogeneous flow as possible over the entire flow channel cross-section with low turbulence. The inlet also reduces the sensitivity to possible false flows of the injection holes, due for example to flow differences and Secondary flows in the pressure chamber arise. Such differences in flow may in particular also arise as a function of the arrangement of the injection holes and the manufacturing tolerances.

Further preferably, at least one of the injection holes is provided along the axes with a convergent - ie a continuously tapered - flow channel. The flow channel cross section change of the convergent flow channel may have a linear or non-linear course. The fuel is accelerated along the flow channel in the injection holes, whereby the pressure level in the region of the inlet of the injection holes and the pressure chamber is raised and high jet velocities are achieved. As a result, cavitation or turbulence is reduced. In particular, the reduction of turbulence and cavitation stabilize the flow in the injection holes and the jet and thus increase the probability of collision of the jets in the combustion chamber.

In addition, at least one of the injection holes along the axes can be configured in regions with a convergent and / or a constant and / or a divergent injection hole cross section, in order to possibly improve the structural mechanical properties of the injector and to enable cost-effective production.

Preferably, a combustion chamber facing sharp-edged formed exit edge of the injection holes. The sharp-edged trailing edge stabilizes the local Entrainment, which in turn supports a homogeneous flow profile. Entrainment describes the ability of a fuel spray in the shear layer to form a mixture with the ambient air. Radiation abstraction or entrainment of the ambient air by the liquid phase of the fuel spray is the result of momentum transfer from the fuel droplets to the ambient air of a fuel spray. The sharp-edged outlet edge is preferably circular.

According to a further preferred embodiment of the present invention, the angle at which the at least two fuel jets intersect along the axes is at most 40 °. Such measured angles of incidence are suitable for forming particularly small droplets due to the effective atomization of the colliding fuel jets. In particular, the spread of the droplets or of the spray and the penetration depth of the spray into the combustion chamber can be influenced by the angle of incidence. Preferably, the angle is between 20 ° and 40 °.

The point of intersection of the at least two axes is preferably at most 20 times the average injection hole cross section or the average injection hole diameter away from the side of the housing or the exit edge facing away from the injector. The injection holes often have a small diameter, so that the distance between the respective trailing edge and the intersection is a maximum of 1 to 2 mm.

Further preferred is a combination of the incident angle of up to 40 ° with the collision of the fuel jets 1 to 2 mm behind the trailing edge of the injection holes, since this arrangement gives the best possible atomization even with generous manufacturing tolerances. In the positioning and dimensioning of the injection holes in the housing of the injector or in a spray perforated disk, the minimum distance from the injection hole to the injection hole must be observed in order to ensure the required mechanical strength.

Moreover, it is particularly advantageous if the injection holes are designed rotationally symmetrical and the injection holes are arranged symmetrically to the longitudinal axis of the closing element or in the housing of the injector in order to reduce possible flow differences in the region of the closing element seat in the pressure chamber. Different inflow conditions of the injection holes can lead to a false flow of these, favor cavitation or turbulence and produce a reduced injection hole filling and an inhomogeneous flow profile.

Preferably, the injection holes are arranged in a housing of the injector and / or in a spray perforated disk. The spray perforated disk can be fixed, liquid and gas-tight coupled to the housing, for example by means of a positive and / or non-positive connection, and allows the exchange of an injection hole configuration of an injector and simplifies its individualization. In addition, the spray perforated plate typically has a simple plate-shaped basic shape, which allows cost-effective production due to good accessibility of the injection holes.

In accordance with a further preferred embodiment of the present invention, the injector also comprises at least one spray-forming injection hole in addition to the injection holes, which intersect at an intersection on the injector-facing side, one axis of which has no intersection on the injector-remote side of the injector with another axis of an injection hole , For this purpose, the at least one spray-forming injection hole may have any shape which is known from the prior art and which is suitable for this purpose best possible atomization of the fuel to allow droplets.

Furthermore, it is also particularly advantageous if the injection holes are introduced by means of an exciting, an electrochemical and / or an abrasive process in the housing and / or spray perforated disc. In particular, the laser drilling method is suitable for the production of the injection holes and the injection hole cross section change. The rounded inlet can be manufactured for example by means of a hydro-erosive manufacturing process.

list of figures

• 1 eine geschnittene Ansicht des erfindungsgemäßen Injektors,
• 2 eine vergrößerte schematische Schnittansicht des erfindungsgemäßen Injektors gemäß 1, und
• 3 eine vergrößerte Darstellung des Schließelementsitzes mit einem der Injektionslöcher gemäß 2.

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

• 1 a sectional view of the injector according to the invention,
• 2 an enlarged schematic sectional view of the injector according to the invention 1 , and
• 3 an enlarged view of the closing element seat with one of the injection holes according to 2 ,

Preferred embodiment of the invention

The following is with reference to the 1 to 3 an injector according to a first preferred embodiment of the invention described in detail.

1 shows a longitudinal section of an injector according to the invention 1 , The injector 1 has one in a housing 3 trained pressure room 4 on, in which a closing element 6 along a longitudinal axis 5 slidably arranged. The pressure room 4 is connected by a high-pressure passage, not shown, with a fuel storage and by this with a fuel 10 filled under a very high pressure. By the movement of the closing element 6 along the longitudinal axis 5 the closing element acts 6 with one on the case 3 trained closing element seat 30 together and opens and closes a first injection hole 21 and a second injection hole 31 , The first injection hole 21 is along an axis 22 and the second injection hole 31 along an axis 32 in the case 3 incorporated.

The shape of the closing element seat 30 corresponds to a on the closing element seat 30 facing free end of the closing element 6 arranged hemispherical closing element head 61 to the injection holes 21 . 31 To close gas and liquid tight. Once the injection holes 21 . 31 through the closing element 6 are released, the pressurized fuel flows 10 from the pressure room 4 through the two injection holes 21 . 31 in the form of a beam 11 from an injector side away 20 in a room 2, for example, a combustion chamber 2 an internal combustion engine (see. 2 ).

The housing 3 is on the the closure element seat 30 opposite end with a housing plate 7 clamped by a clamping device, not shown, so that the housing plate 7 the pressure room 4 limited. Between the closing element 6, the housing plate 7 and a sleeve 70 in which the closing element seat 30 facing away from the end of the closing element 6 is guided longitudinally movable, is a control room 71 educated. The closing element 6 is by means of a spring 60 on the sleeve 70 supported and thus biased, so that the closing element 6 pressed against the closing element seat 30.

The pressure in the control room 71 that the closing element head 61 the closing element 6 together with the spring 60 against the closing element seat 30 is pressed, is controlled by a control device, not shown. The controller thus determines the pressure state in the control room 71 and indicates the position of the closing element 6 along the longitudinal axis 5 in front.

The axes 22 . 33 the two injection holes 21 . 31 are aligned at an angle of 40 ° to each other and intersect on the side facing away from the injector 20 in an intersection 37 , At the exit of the fuel 10 from the injection holes 21, 31 by a sharp exit edge 36 initially form two rays 11 those in the intersection 37 completely collide with each other and a spray of a variety of droplets 12 form. In the edge region of the jet 11 and of the spray emerge, partly by displacement, partly by shear forces with the ambient air, so-called torus vortices, which lead ambient air to the droplet-air mixture. Due to the pressure difference inside and outside the jet 11 and the spray ambient air is sucked into it (Entrainment-flow) and promotes an additional mixing of the droplets 12 with the ambient air.

2 is a sectional view of the injector according to the invention 1 in an enlarged sectional view in the region of the closing element seat 30 to remove the housing 3.

The pressure room 4 , the closing element 6 and the closure member seat 30 are as cylindrical formed rotationally symmetrical components and are coaxial with the longitudinal axis 5 aligned.

In the case 3 are symmetrical to the longitudinal axis 5 the first injection hole 21 with the first axis 22 and the second injection hole 31 with the second axis 32 incorporated. The injection holes 21 . 31 are in the area of the pressure chamber 4 in the case 3 introduced, by the interaction of the closing element 6 and closing element seat 30 for injecting the fuel 10 can be opened and closed. The injection holes 21, 31 connect the pressure chamber 4 with the injector side 20 or the combustion chamber 2 by means of a flow channel 34 , On the pressure chamber 4 facing side of the housing 3 the respective injection holes 21, 31 an inlet 33 on, through which the fuel 10 in the open position of the closing element 6 in the respective injection hole 21 . 31 can flow in. The fuel 10 then flows through the flow channel formed by the respective injection hole 21, 31 34 in the direction of the injector side facing away 20 and leaves the respective injection hole 21 . 31 through the trailing edge 36 as a ray 11 ,

The axes 22 . 32 the injection holes 21 . 31 are for the effective atomization of the fuel 10 aligned at an angle of 40 ° and thus intersect at an intersection 37 on the injector side 20 of the injector 1 with an impact angle of 40 °. The point of intersection 37 is coaxial on the longitudinal axis 5 of the housing 3 arranged and a distance a of the point of intersection 37 to the respective exit edges 36 is in function of the injection hole 21 to injection hole 31 Distance maximum 2mm (cf. 3 ).

So that the two rays 11 collide completely and the required atomization degree is achieved, reject the rays 11 mutually corresponding shapes generated by identical injection hole geometries.

Due to the complete collision of the two beams 11 in the area of the intersection 37, the two rays become 11 to microscopic droplets 12 atomized. The droplets 12 spread in the room 2 and mix with the air there as a spray for the combustion process.

The injector 1 further comprises a spray-forming injection hole 41 with an axis 42 that does not intersect 37 with one of the axles 22 . 32 one of the other injection holes 21 . 31 of the injector 1 having. The spray-forming injection hole 41 has a constant flow channel cross section 35 and the fuel 10 decays behind the trailing edge 36 to a variety of spray-forming droplets 12 , The flow channel 34 of the spray-forming injection hole 41 may of course also have any known from the prior art flow channel shape or any flow channel course, depending on the purpose of the spray-forming injection hole 41 , For example, the penetration depth of the spray and the spray propagation angle is designed.

The enlarged view in 3 can be used for the stabilization of the beam 11 necessary embodiment of the injection holes 21 . 31 be removed. The injection holes 21 . 31 are for this purpose in a spray perforated disk 38 incorporated, the modular and interchangeable in the injector 1 can be used. The spray perforated disk 38 is gas-tight and liquid-tight with the housing 3 connected, and provides the injection holes 21 . 31 for the injector 1 to disposal.

The enema 33 the injection holes 21 . 31 is optimized with a trumpet or bell-shaped rounding, which is characterized by the fact that these deletions, cavitation and pressure losses in the area of the inlet 33 prevents or minimizes and forms a particularly homogeneous flow profile in the injection holes 21, 31. The enema 33 increases the flow channel cross section 35 at the inlet 33 opposite the respective flow channel cross section 35 of the injection holes 21 . 31 and its trailing edge 36 and forms an edge-free and smooth transition from the pressure chamber wall to the flow channel of the injection holes 21 . 31 ,

The enema 33 reduces the influence of false flows, ie flows whose flow vectors in the area of the inlet 33 not parallel to the respective axis 22 . 32 are aligned. Fehlanströmungen lead to an inhomogeneous flow profile in the injection wells 21 . 31 and thus destabilize the beam 11 , The enema 33 can by means of a hydroerosive process in the injector 1 or in the housing 3 be incorporated.

The flow channel cross section 35 the injection holes 21 . 31 tapers along the axes 22 . 32 in the flow direction and the area flowed through perpendicular to the flow direction decreases steadily. Consequently, the flow channel cross section 35 of the trailing edge 36 opposite the flow channel cross section 35 of the inlet 33 measured smaller. This geometry of the injection holes 21 . 31 corresponds to a convergent nozzle. By the rounding of the inlet and the continuous taper of the injection hole cross-section 35 along the injection hole axes 32 in the direction of the combustion chamber 2 is the cavitation or turbulence reduced and consequently the injection hole filling - so the effective Fuel mass flow through the injection holes 21, 31 - increases. This combination of measures leads to a homogeneous flow profile and has a stabilizing effect on the jet 11 out.

On the side away from the injector 20 the injection holes 21 . 31 the exit edge 36 is sharp-edged. The sharp-edged trailing edge 36 stabilizes the local entrainment, which also supports the homogenization of the flow profile.

It goes without saying that the number of injection holes 21 . 31 can be chosen arbitrarily high. The rays generated thereby 11 of the injector 1 can be in an intersection 37 or meet in several different points of intersection 37. The injection holes 21 . 31 can do this axisymmetric on the longitudinal axis 5 or be arranged symmetrically in a plane along the longitudinal axis 5. For example, the injector 1 four rays 11 exhibit that are in an intersection 37 or in pairs in two different intersections 37 cross. In addition, it goes without saying that the injector according to the invention 1 for injecting any liquid medium into a room 2 can be used.

Thus, according to the invention, an injector 1 be provided, which significantly improved atomization of the fuel 10 has despite reduced manufacturing tolerances and / or a reduced injection pressure.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102014202687 A1 [0002]

Claims (10)

Injector (1), in particular a fuel injector (1), comprising: at least one first injection hole (21) having a first axis (22) and a second injection hole (31) having a second axis (32) for introducing fuel (10), - Wherein at least the first and the second axis (22, 32) intersect on an injector side facing away from (20) of the injector (1) in an intersection (37), and - Wherein at least one injection hole (21, 31) has a rounded inlet (33), a tapered flow channel (34) and a sharp-edged outlet edge (36). Injector after Claim 1 , characterized in that a cross section of the first and second injection hole (4, 31) is the same in each case. Injector (1) after Claim 1 or 2 , characterized in that the inlet (33) of the injection holes (21, 31) has a trumpet or bell-shaped rounding. Injector (1) according to one of the preceding claims, characterized in that at least one of the injection holes (21, 31) along the axes (22, 32) at least partially a convergent and / or constant and / or divergent flow channel (35). Injector (1) according to one of the preceding claims, characterized in that the at least two cutting axes (22, 32) of the injection holes (21, 31) intersect an angle of at most 40 °. Injector (1) according to one of the preceding claims, characterized in that the distance (a) between the intersection (37) and the outlet edge (36) corresponds to a maximum of 20 times the mean flow channel cross-section (35). Injector (1) according to one of the preceding claims, characterized in that the injection holes (31) are rotationally symmetrical and that the injection holes (31) are arranged symmetrically on a longitudinal axis (5). Injector (1) according to one of the preceding claims, characterized in that the injection holes (21, 31) are arranged in a housing (3) or in a spray perforated disk (38). Injector (1) after Claim 8 , characterized in that the injection holes (21, 31) by means of laser drilling, a cutting, electrochemical and / or an abrasive manufacturing process in the housing (3) or in the spray perforated disk (38) are incorporated. Injector (1) according to one of the preceding claims, characterized in that the injector (1) comprises at least a third spray-forming injection hole (41) whose axis (42) no intersection (37) on the injector side facing away (20) with an axis ( 22, 32) of another injection hole.

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