DK2504561T3

DK2504561T3 - Fuel injection nozzle for burning power machines

Info

Publication number: DK2504561T3
Application number: DK10781443T
Authority: DK
Inventors: Gerhard Beier; Ilona Gostic; Michael Hekel; Axel Löffler; Horst Ressel; Ralf Schüle; Holmer Slocinski; Robert Haubold; Marco Wyszkowski
Original assignee: Orange Gmbh
Priority date: 2009-11-25
Filing date: 2010-11-23
Publication date: 2015-04-20
Also published as: WO2011063929A1; DE102009054441A1; KR101682346B1; EP2504561B1; CN102725511B; CN102725511A; KR20120086738A; EP2504561A1

Description

The invention relates to a fuel injection nozzle for internal combustion engines, in particular auto-ignition internal combustion engines, according to the preamble of Claim 1, as shown e.g. in DE 39 38 551.

Injection nozzles which have a similar basic structure, in particular also as parts of injectors, are known in various configurations . DE 32 27 742 A1 thus shows an injection nozzle in which the nozzle needle guided with a shank section in a longitudinal bore of a guide body has, adjoining this shank section, a cylindrical shank section which has a reduced diameter and passes through the pressure space and the fuel supply to the pressure space is carried out axially on the face side. Also on the face side to the pressure space, the guide body is formed with a an "annular collar", which encompasses the projection of the shank section which has a reduced diameter to the guided shank section, as a guide part for a helical spring which is supported on the guide body and axially acts upon the nozzle needle in the direction of its closed position. EP 1 026 393 A2 further shows, as part of an injector, an injection nozzle with a control body which adjoins a nozzle body. Nozzle bodies and control bodies are provided centrally with bores which form an axial transition into one another for the nozzle needle and a pressure piston which is situated in the control body and is connected to the nozzle needle via a pressure rod. The pressure rod passes through a pressure space to which, on the circumferential side, i.e. radially from the outside, a fuel supply channel leads, and indeed in the axial transition region between control body and nozzle body such that these delimit regions of the fuel supply channel and of the pressure space which are open to one another, to that part of which assigned to the control body the axial bore which accommodates the control piston leads, in the case of a position of the pressure piston which is offset in a stepped manner in the closed position of the nozzle needle adjoining the outlet. As a result of the radial alignment of the fuel supply channel to the pressure space, notch stresses at the outlet point should be avoided, moreover high high-pressure and fatigue strength should be achieved.

In the case of a fuel injection valve according to DE 196 11 884 Al, the nozzle body is also formed with a guide bore tapering off to the pressure space for the nozzle needle which has a shank section running in the guide bore, which shank section forms a run-in transition into the pressure space into a shank section with a reduced diameter. As a result a gaplike annular space which is open with respect to the pressure space is generated tapering off to the guide bore between it and the shank of the nozzle needle. This serves, in the case of a fuel supply channel running in to the pressure space at an acute angle to the nozzle needle and adjacent to this, to relieve the intermeshing region of the nozzle body remaining between the guide bore and the fuel supply channel in that corresponding counterforces can be built up in a superimposed manner on the pulsating pressure forces in the fuel supply channel proceeding from the pressure space in the gap-like annular space.

Also in the case of EP 0 961 024 Al, which shows a fuel injection nozzle for a two-stroke large diesel engine, and in the case of which the fuel supply is controlled via two nozzles located one behind the other. In order to be able to configure the second nozzle, which controls the injection openings with its nozzle needle, with as small as possible a blind hole volume and as a result prevent delayed dripping, the nozzle needle of the second nozzle has a stepped diameter. The shank section with a larger diameter of the nozzle needle lies in a guide bore and forms a transition in the outlet region of the guide bore to the pressure space to the smaller shank section with a smaller diameter. The supply of fuel to the pressure space is also carried out here via fuel supply channels running at an acute angle to the nozzle needle and running in adjacent to the outlet region to the pressure space so that at risk intermeshing regions to be relieved by two-sided pressure actuation are produced.

Comparable conditions are also present in the case of an injection nozzle which is apparent from JP 58-13154 A.

Fuel injection nozzles which correspond to the preamble of Claim 1 in terms of the basic structure are known, for example, from DE 39 38 551 A1. In the case of high injection pressures which are increasingly used in operation, such injection nozzles are at risk of cavitation, in particular in the case of formation of local pressure differences. A zone which is critical in this regard is the transition region from the shank section, which is guided in the longitudinal bore of the nozzle body, of the nozzle needle to its shank section which has a reduced diameter and passes through the pressure space. Pressure differences which arise in association with the substantially radial incoming flow of the part, which projects into the pressure space, of the shank section corresponding to the guide section and the cambered pressure shoulder, which adjoins the guide section, of the constricted shank section result, as practice has shown, in a low-pressure zone which can lead to cavitation damage in the part, which forms a transition to the pressure shoulder, of the shank section which corresponds to the guide section.

It is known from DE 195 15 936 Al, in relation to similar through-flow conditions for a constricted shank section, which follows on from a guided shank section, of a valve needle of a through-flow means control device, to achieve spiral line or helical line shaped flowing around of the valve shaft by tangential incoming flow of the pressure space in order to avoid local pressure differences and any resultant cavitation damage.

The object on which the invention is based is to propose a formation for a fuel injection nozzle of the above-mentioned type, with which formation cavitation damage can be avoided particularly in the region of the transition from the shank section, guided in the guide section of the longitudinal bore, of the nozzle needle to its constricted shank section.

This is achieved with the features of Claim 1. The subordinate claims contain expedient further developments.

Taking into account the specified configuration features and dimensions, an annular space delimited radially to the outside and axially open with respect to the pressure space is produced tapering off from the guide section of the longitudinal bore, in which annular space a fluid ring which is largely balanced at least in terms of the pressure conditions and is at a lower pressure than the pressure peaks in the pressure space can be formed.

This results in a gradual pressure transition from the pressure space to the annular gap between the shank section of the nozzle needle and the guide section of the longitudinal bore. This produces a certain protection function, on one hand, against the formation of gas bubbles in the transition from the pressure space to the annular gap and in the annular gap, and on the other hand also in terms of the implosion, which causes cavitation damage, of gas bubbles exiting out of the annular gap when the nozzle needle is opened. The formation of gas bubble is thus initially at least reduced and on the other hand a larger fluid volume than in the annular gap is also available for gas bubbles exiting from the annular gap to the annular space on opening of the nozzle needle within the annular space so that it is very difficult for implosions close to the walls to arise. The drop in pressure which arises running in the direction of the annular gap, corresponding to the cross-sectional reduction of the annular space with respect to the annular gap, is important for the at least to a large extent avoidance of cavitation damage.

This cross-sectional reduction is determined by the small distance, which corresponds to a third of the diameter of the longitudinal bore, from the transition of the guide section of the longitudinal bore to the pressure space to the adjacent end of the guided shank section of the nozzle needle and the angle of taper, which is around 70°, of the constricted shank section. A reduction in the pressure differences in the pressure space is furthermore to be achieved by the fuel supply to the pressure space in a radial overlap with the waist of the constriction, thus also, in combination with the asymmetric incoming flow of the nozzle needle. Such a configuration is to be realized without a substantial reduction in the length of the guided shank section or an extended nozzle structure.

Further details and features of the invention will become apparent from the description, the claims and the drawings. In the drawings :

Fig. 1 shows, in a simplified representation, a cross-section through a fuel injection nozzle, and

Fig. 2 shows, in an enlarged representation, the section, which tapers towards the blind hole bore proceeding from the waist to the needle tip, of the shank of the nozzle needle.

The part, which injects to the combustion chamber of the internal combustion engine, not shown, of an injection nozzle 1 for fuels, in particular diesel fuels, is schematically represented in Fig. 1, which part can in particular also be a component of a fuel injector. Injection nozzle 1 has a nozzle body 2 which has a longitudinal bore 4 running in the direction of its longitudinal axis 3 with sections of a different diameter. Longitudinal bore 4 accommodates a nozzle needle 5 and tapers towards injection openings 6 provided in the combustion chamber-side end of nozzle body 2.

Nozzle needle 5 has a shank section 7, where applicable, provided with micro-grooves, with which section it is guided axially displaceably in a guide section 8 of longitudinal bore 4 of nozzle body 2 in the direction of longitudinal axis 3. Said guide section 8 leads to a part, which has an extended diameter and is formed as pressure space 9, of longitudinal bore 4, which part a further section 10 of longitudinal bore 4 adjoins which tapers via a bore-side seat surface 11 towards injection openings 6. 12 designates an axially running fuel supply channel which leads radially to pressure space 9, wherein the supply of fuel in the exemplary embodiment is carried out via two outlet openings 13 asymmetrically to pressure space 9, through which a shank section 14, which adjoins guided shank section 7 and is radially constricted, of nozzle needle 5 passes. A further shank section 15, which has a reduced diameter in comparison to shank section 7 and delimits an annular space 16 to the circumference of longitudinal bore 4, via which the supply of fuel is carried out from pressure space 9 in the direction of seat surface 11 of nozzle body 2, adjoins constricted shank section 14 running over the profile of longitudinal axis 3, for which nozzle needle 5 has a corresponding sealing surface 18 adjacent to its nozzle needle tip 17.

In the case of nozzle needle 5 located in the closed position, the inflow of fuel to injection openings 6 is blocked via surfaces 11 and 18 which adjoin one another. If nozzle needle 5 is lifted out of its seat, fuel is injected via injection openings 6 to the respective combustion chamber, in the case of supply of fuel via outlet openings 13 to pressure space 9 in the region of waist 19 of constricted shank section 14. Waist 19 radially overlaps with outlet openings 13 which are arranged asymmetrically offset to longitudinal axis 3 and offset to one another in the circumferential direction in relation to the circumference of pressure space 9 so that, as a result of flow, at least over the circumferential region of pressure space 9, regions which are at a different pressure level are produced. In the case of corresponding pressure differences, this can lead to the formation of cavitation bubbles in the respective low pressure regions which can lead to damage of the respective surface in the case of implosion close to the wall in the higher pressure region. Such damage is critical in particular in shank section 7, which is guided in longitudinal bore 4, of nozzle needle 5, above all when it occurs at nozzle needle 5.

According to the invention, at least substantial protection of this region against cavitation damage is achieved in that shank section 7 guided in longitudinal bore 4 of nozzle body 2 ends spaced apart to the outlet of longitudinal bore 4 to pressure space 9 which is radially extended with respect to longitudinal bore 4, therefore that the transition between shank section 7 guided in longitudinal bore 4 and in this regard constricted shank section 14 is located in front of the inlet of guide section 8 of longitudinal bore 4, and thus within guide section 8 of longitudinal bore 4. As a result of this, an annular space 20, in particular a flat triangular annular space 20, is produced running in from pressure space 9 to guide section 8 in an enclosing manner to the connection region of constricted shank section 14 to guided shank section 7. As a result of the gradual cross-sectional transitions from pressure space 9 to the annular gap between shank section 7 and guide section 8 which avoids jumps in pressure or at least reduces them, the fluid ring formed in annular space 20 is to be understood functionally as a "protective ring" against the creation of cavitation bubbles in the transition to the annular gap and in the annular gap, which also leaves the required space for gas bubbles exiting out of the annular gap on opening of the nozzle needle for any potential implosion of said bubbles in the region distant from the wall so that cavitation damage to the nozzle shank is at least largely avoided.

Irrespective of the explanation, which is based partially on theoretical considerations, of the effect according to the invention, the formation according to the invention has been shown to be productive in practice and to be suitable for at least substantially avoiding cavitation damage in the region in question.

In the context of the invention, it has been shown to be expedient and sufficient if distance 21 of guided shank section 7 of nozzle needle 5 from the transition of longitudinal bore 4 of nozzle body 2 to pressure space 9 corresponds to a fraction of diameter 22 of guide section 8 of nozzle body 2. One preferred scale is that the size of distance 21 is located at a third of diameter 22 of longitudinal bore 3. This in combination with an angle of taper 24 in the region of 70° so that a comparatively flat cross-section of triangular annular space 20 is produced.

In particular in combination with such scales, a waist diameter 23 which is greater than half the diameter of the guide section of longitudinal bore 4 located in nozzle body 2, and in particular is located at approximately two-thirds of diameter 22 of guide section 8 of the longitudinal bore and thus also of the diameter of guided shank section 7 has been shown to be expedient for constricted shank section 14.

In the enlarged representation of the part of nozzle needle 5 tapering to nozzle needle tip 17 according to Fig. 2, the region around nozzle needle tip 17 is shown in addition to the representation according to Fig. 1 and the reference numbers used there as well as the illustrations of this. It is thus demonstrated that needle-side sealing surface 18 which corresponds to seat surface 11 on nozzle body 2 is located between a truncated cone-shaped annular region 25, which adjoins shank section 15 and tapers with regard to nozzle needle tip 17, and nozzle needle tip 17, wherein respective angles of taper 26 to 28 are indicated for truncated cone-shaped annular region 25, annular sealing surface 18 and nozzle needle tip 17. The respective angle size of these reduces proceeding from angle of taper 26 of nozzle needle tip 17, wherein the preferred values are for angle of taper 26 of nozzle needle tip 17 120°, for angle of taper 27 of sealing surface 18 90° and for angle of taper 28 - as what is known as a pre-angle - of annular region 25 75°. This in combination with a configuration of the injection nozzle according to Fig. 1, in the case of which portion 10 of the longitudinal bore which accommodates shank section 15 and delimits annular space 16 ends at the height of annular region 25 and tapers with regard to annular region 25 in a constricted manner, in particular in a step. The fuel supplied via annular space 16 is thus introduced at the height of annular region 25 across the annular gap provided for nozzle body 2 and tapering towards seat surface 11 of nozzle body 2, the annular gap between seat surface 11 and sealing surface 18 as well as nozzle needle tip 17 into the blind hole bore from which injection openings 6 proceed. The transition running in a stepped manner for the fuel supply carried out across annular space 16 to the blind hole enables good control of the flow conditions .

List of reference numbers 1 Injection nozzle 2 Nozzle body 3 Longitudinal axis 4 Longitudinal bore 5 Nozzle needle 6 Injection opening 7 Shank section 8 Guide section 9 Pressure space 10 Section 11 Seat surface 12 Fuel supply channel 13 Outlet opening 14 Shank section 15 Shank section 16 Annular space 17 Nozzle needle tip 18 Sealing surface 19 Waist 20 Annular space 21 Distance 22 Diameter 23 Waist diameter 24 Angle of taper 25 Annular region 26 Angle of taper 27 Angle of taper 28 Angle of taper

Claims

1. Fuel injection nozzle for internal combustion engines, in particular self-igniting internal combustion engines, having a longitudinal bore (4) accommodating a nozzle needle (5) and extending in a nozzle body (2) and extending from a guide section (8) of the nozzle needle (5) through a region extended to a pressure chamber (9) extends to at least one injection port (6), wherein the nozzle needle (5) has a guide shaft portion (7) corresponding to the guide portion (8) and there as a connection to that shaft portion (15) extending to the seat of the nozzle needle joins a diameter-lined shaft portion (14) which penetrates the pressure chamber (9) to which, at the circumferential side, at least one fuel supply (12), characterized by the shaft portion (8) of the nozzle body (5) in the guide portion (8) of the nozzle needle (5) related to its closed position ends at a distance from the passage of the longitudinal bore (4) to the pressure space (9) within the longitudinal bore (4), distance is at one third of the diameter (22) of the longitudinal bore (4) and the constricted shaft portion (14) joins the leading shaft portion (14) at a cone angle (24) about 70 °, the fuel supply (12) opening into the pressure chamber (9) radially overlap the waist portion (14) of the lined shaft section (14).

Fuel injection nozzle according to claim 1, characterized in that the diameter (23) of the waist (19) of the lined shaft section (14) is larger than half the diameter (22) of the longitudinal bore (4).

Third

Fuel injection nozzle according to one of the preceding claims, characterized in that the diameter (23) of the waist (14) of the lined shaft section (14) lies at two thirds of the diameter (22) of the longitudinal bore (4).