EP2824311A1 - Piston element assembly, and fuel injector with a piston element assembly - Google Patents

Abstract

A piston element arrangement, in particular for a fluid injection nozzle (1), comprises a piston element (7) with at least one guide section (7a) and a central axis (7e); and a bore (9), in which the at least one guide portion (7a) of the piston element (7) is guided longitudinally displaceable. The piston element assembly has at least one surface structure (10) with a number of axially spaced discontinuous circumferential structures. An injection nozzle (1) is equipped with the piston element assembly.

Description

The invention relates to a piston element arrangement, in particular for an injection nozzle. The invention also relates to an injection nozzle with such a piston element arrangement.

A piston element arrangement generally comprises a piston element and a bore, in which the piston element is guided longitudinally displaceably with a guide section. Such piston element arrangements are e.g. Pistons with piston guides, as well as e.g. Cylinder walls of pumps, especially high-pressure pumps, and in injectors possible.

Injectors inject fluid substances, in particular fuels, under (high) pressure from an injection pump or a common rail system into the combustion chamber of an internal combustion engine, e.g. air-compressing, self-igniting internal combustion engines such as diesel engines.

There are different types of injectors, of which the so-called hole nozzle should be considered here. The hole nozzle is used in internal combustion engines with direct injection, since with her a particularly fine distribution of the fuel is achieved. Hole nozzles are designed as a single-hole and multi-hole nozzles. One-hole nozzles have a spray hole, which is arranged in the direction of the nozzle axis or laterally thereof.

The document EP 2 365 207 A1 illustrates an injection nozzle for an internal combustion engine.

Usually, in the guide region of cylindrical, oscillating guide sections of piston elements continuous concentric grooves are arranged at a small distance from each other. This should be achieved centering and less wear of the guide surfaces. Mainly such grooves in piston-shaped elements of pneumatic and hydraulic valves and pressure generators for fluids, e.g. Gases and liquids of any kind used. These designs have proven themselves in practice.

There is a continuing need to increase the life of piston element assemblies in different applications.

Therefore, the object of the present invention is to provide an improved piston element assembly.

The object is achieved by a piston element arrangement with the features of claim 1.

The object is also achieved by an injection nozzle having the features of claim 15.

Accordingly, a piston element arrangement, in particular for a fluid injection nozzle, comprises a piston element with at least one guide section and a central axis; and a bore in which the at least one guide portion of the piston member is guided longitudinally displaceable. The piston element assembly has at least one surface structure with a number of axially spaced discontinuous circumferential structures.

The surface structures are provided with defined, interrupted, circumferential structures. As a result, in contrast to the prior art, it is advantageously possible to have turbulences in the guide areas on these surface structures generate flowing past medium, which allow an improved centering of the guide surfaces and reduced wear. This also means a longer life.

Another advantage is that in addition to the improved leadership and a sealing effect is achieved, which can reduce leakage oil reflux and optimal lubrication can be ensured.

An injection nozzle according to the invention, in particular a hole nozzle for an internal combustion engine, comprises a body; a piston member assembly comprising a piston member formed as the nozzle needle and a bore in the body in which the piston member is slidably guided; a pressure chamber communicating with an inlet bore and a passage with a spray chamber, the passage having a sealing seat for cooperation with a sealing tip of the piston element; and at least one spray hole through which the spray chamber communicates with the outside of the body. The injector has the above piston element arrangement.

In one embodiment, each of the axially spaced discontinuous circumferential structures includes indentations and / or plaques spaced from discontinuities having no indentations or plots, the indentations and / or plots and interruptions one behind the other at the periphery of an imaginary circular plane , which is perpendicular to the central axis, are arranged annularly. An advantage here is that the turbulence can be generated in a simple manner by the alternating arrangement of interruptions and indentations or applications.

In this case, each indentation and / or application of the axially spaced-apart discontinuous, circumferential structures has a structure length and the interruption arranged between two indentations has a structure spacing, the structure length, the structure spacing and an axial spacing of the interrupted, circulating structures being equal or different from one another Have dimensions. For a simple adaptation by the geometric parameters to different applications is possible. For example, the structure length may have a dimension in a range of about 0.25 ... 5 mm. The structural width of a molding or a plot may, for example, have a dimension in a range of about 0.02 ... 2 mm.

In a further embodiment, a structure depth of an indentation or a height of a plot may be approximately 0.1 to 2 times the structure width.

In addition, a cross-section of indentation or / and a plot may be rectangular, pointed or conical, round or oval, or in a combination thereof. This results in the advantage of a further increase in the range of application.

The at least one surface structure may be obtained by means of a beam removal process, e.g. Laser, and / or a material application process are produced. Thus, for example, with cockroaches, embossing, pressing, coating and the like. create the structures in a quick and easy way.

In one embodiment, the at least one surface structure is arranged on the guide section of the piston element. The piston element can therefore also be easily retrofitted.

If the at least one surface structure on the guide portion of the piston element has a diagonal structure such that a rotational movement of the piston element can be generated when flowing around with a medium, there is the advantage that a seated impact, e.g. can be prevented or significantly reduced in an injection nozzle.

In an alternative embodiment, the at least one surface structure is arranged on a bore surface of the bore. So also conventional piston elements can be used.

In a further alternative embodiment, at least one surface structure is arranged on the guide section of the piston element, and at least one surface structure is arranged on a bore surface of the bore. This results in further design freedom for further applications, e.g. special media, certain medium pressure.

In this case, the at least one surface structure on the guide portion of the piston element and the at least one surface structure on the bore surface of the bore opposite, axially spaced or overlap. This continues to increase design and customization options.

In one embodiment, the injection nozzle has an outer surface of a nozzle tip of the body with a surface finish, which is designed as a fine polishing with a certain degree of fineness, preferably with a surface roughness of about Rt ≤ 1.7. This results in the advantage of reduced coking and vitrification of the areas of the injection holes of the injection nozzle during operation, a longer life is the result.

The injection nozzle according to the invention can be used both for use for the injection of fuels in powdered, liquid or gaseous form in the combustion chamber of combustion units, such as internal combustion engines, as well as for use for the atomization of powdery, liquid or gaseous media.

Fig. 1

eine schematische Teilschnittdarstellung einer erfindungsgemä-ßen Einspritzdüse als Lochdüse mit einer erfindungsgemäßen Kolbenelementanordnung;

Fig. 2

eine schematische, vergrößerte Teildarstellung einer erfindungs-gemäßen Oberflächenstruktur nach Fig. 1;

Fig. 3-3e

schematische vergrößerte Darstellungen von erfindungsgemäßen Oberflächenstrukturen; und

Fig. 4

schematische vergrößerte Schnittdarstellungen von erfindungs-gemäßen Oberflächenstrukturen.

The invention will now be explained in more detail by means of embodiments with reference to the accompanying drawings. Hereby show:

Fig. 1

a schematic partial sectional view of an inventive injection nozzle as a hole nozzle with a piston element arrangement according to the invention;

Fig. 2

a schematic, enlarged partial representation of a fiction, according to the surface structure Fig. 1 ;

Fig. 3-3e

schematic enlarged representations of surface structures according to the invention; and

Fig. 4

schematic enlarged sectional views of inventive surface structures.

Identical components or functional units with the same function have the same reference numerals in the figures.

The terms "top" and "bottom" are locations that refer to the respective figure representation.

Fig. 1 shows a schematic partial sectional view of an injection nozzle 1 according to the invention as a hole nozzle with a piston element arrangement according to the invention. The piston element arrangement comprises a piston element 7 and a bore 9, in which the piston element 7 is guided longitudinally adjustable. The Piston element arrangement is described here by way of example in the application of an injection nozzle 1, but is not limited to an injection nozzle 1.

The piston element 7 is provided with surface structures 10 according to the invention, the piston element 7 being designed here as a nozzle needle. The injection nozzle 1 is shown in the closed position.

In this embodiment, the injection nozzle 1 is provided for a high-pressure injector used in an internal combustion engine, and liquid fuel, e.g. Diesel fuel, used as a fluid medium.

The injection nozzle 1 comprises a body 2 and the piston element arrangement with the piston element 7 and the bore 9. The body 2 has an in Fig. 1 Above drawn upper part of the injection nozzle 1 has a circular cross-section, in which the piston member 7 in the bore 9 is arranged longitudinally movable and rotatable. The bore 9 passes into a pressure chamber 5 formed in the body 2. The pressure chamber 5 is connected at its upper end to an inlet bore 4.

The inlet bore 4 is arranged next to the bore 9 in the body 2 and opens at its lower end into the pressure chamber 5, which narrows down to an unspecified passage. The passage 9 has a conical seal seat and finally opens into a spray chamber 6, which is located in a formed in the lower end of the body 2 nozzle tip 3 of the injection nozzle 1.

The nozzle tip 3 is here hemispherical in shape, with one wall of the nozzle tip 3 having injection holes 8 which extend out of a rounded bottom of the injection chamber 6 through the wall of the nozzle tip 3 to the outside and open into an outer surface 3a of the nozzle tip 3.

The outer surface 3a of the nozzle tip 3 has a surface treatment 3b. The surface treatment 3b is here designed as a fine polish with a certain degree of fineness. This prevents or reduces the coking and / or glazing of the areas of the outer surface 3a of the nozzle tip 3 around the spray holes 8. The fineness of the surface treatment 3b has, for example, a value of a roughness of Rt ≤ 1.7.

The piston element 7 has a guide section 7a, an inlet section 7b, a sealing tip 7c, a guide surface 7d and a central axis 7e.

The guide portion 7a of the piston member 7 is longitudinally movably held and guided in the bore 9 and is provided with an upper end which protrudes from the bore 9 from the upper end of the body 2 of the injection nozzle 1. In addition, the piston member 7 is rotatable about the central axis 7e. The guide portion 7 extends along the central axis 7e of the piston element 7 substantially completely in the bore 9 and is connected at its lower end to the inlet section 7b.

The inlet section 7b of the piston element 7 extends through the pressure chamber 5 into the passage into the injection chamber 6. In this case, the piston member 7 tapers to the conical sealing tip 7c, which cooperates with the conical seal seat in the passage as a tight valve seat.

The piston element 7 is here as a nozzle needle by means of a drive, not shown, e.g. mechanically, electromagnetically or by increasing pressure of fuel in the pressure chamber 5, along the central axis 7e longitudinally adjustable. To open the seal seat, the piston member 7 is moved by this drive upwards. The conical sealing tip 7c then releases the seal seat. The medium, here fuel, which is under pressure in the pressure chamber 5 and also replenished under pressure through the inlet bore 4, now flows from the pressure chamber 5 through the passage into the injection chamber 6 and from there through the injection holes 8 each as an injection jet to the outside in the combustion chamber of an internal combustion engine, not shown.

When closing the injection nozzle 1, the piston member 7 is moved down again, the sealing tip 7c passes back into the seal seat. In this case, a certain, so-called impact force of the sealing tip 7c on the seal seat of the body 2 occur.

The guide portion 7a, the piston member 7, the guide surface 7d on its outer side. The guide surface 7d is provided in this embodiment with three areas, each having a surface structure 10, which will be described in more detail below.

In Fig. 2 is a schematic, enlarged partial view of the surface structure 10 according to the invention Fig. 1 shown.

An enlarged portion of the guide portion 7a of the piston member 7 in a portion of the bore 9 is shown. Between a bore surface 9 a of the inner wall of the bore 9 and the outer surface 7 d of the guide portion 7 a, a gap 9 b is formed, which is filled by the medium which is injected through the injection nozzle 1. At the top of the shown portion of the guide portion 7a, there is a medium pressure P1, and at the bottom, a medium pressure P2.

The area of the surface structure 10 on the guide surface 7d of the piston element 7 has an axial length b in the direction of the central axis 7e. The reference symbol a indicates an axial length of a region without a surface structure 10.

In the Fig. 2 shown surface structure 10 has interrupted, defined structures whose structure and forms are explained in more detail below. In this example, the surface structure 10 consists of eleven circumferentially spaced, circumferentially arranged guide surfaces 7d of the guide section 7a of the piston element 7 arranged axially spaced.

Such a discontinuous circumferential structure has recesses, e.g. Notches, into a material from a surface of the material and / or deposits protruding from that surface of the material, which are spaced from interruptions having neither indentations nor plots. The indentations and interruptions are arranged in a row on the circumference of an imaginary circular plane, which runs at right angles to the central axis 7e.

The broken, circumferential structures are still below in connection with the FIG. 3 explained in detail.

A distance (starting from the top) in the axial direction between the first and the second interrupted circumferential structures is denoted by c. A distance d denotes the axial distance of the second and third interrupted circumferential structures, wherein the designation e indicates the distance between the third and fourth interrupted circumferential structures is. The distances c, d, e may have the same size or be different.

These defined, discontinuous circumferential structures of the surface structure 10 create turbulence 12 in the medium flowing past them in the space 9b. These turbulences 12 enhance centering of the guide portion 7a and thus the piston member 7 in the bore 9, reducing wear by providing a liquid - / Fluid film a hydrodynamic sliding bearing between the guide surface 7 d of the guide portion 7 a of the piston member 7 and the bore surface 9 a of the inner wall of the bore 9 form. In this way, a sealing function is also possible. In addition, so-called leakage oil refluxes are avoided. By the liquid / fluid film also optimal lubrication between the guide portion 7a of the piston member 7 and the bore 9 of the body 2 is ensured.

A rotational movement of the nozzle needle 7 about its central axis 7e is denoted by the reference numeral 11, wherein a longitudinal movement direction 13 of the piston element 7 extends in the direction of its central axis 7e. The longitudinal movement direction 13 is indicated by a double arrow, since the longitudinal movement of the piston element 7 is oscillating.

In the FIGS. 3 to 3e schematic enlarged representations of surface structures 10 according to the invention are shown in a projection plane. In this case, the respectively associated central axis 7e extends perpendicular to the drawings from top to bottom.

The surface structure 10 can be arranged both on the guide surface 7d of the guide section 7a of the piston element 7 and on the bore surface 9a of the bore 9 (or also on both surfaces 7d and 9a). For this reason are in the FIGS. 3 to 3e the reference numerals, which refer to the corresponding portions of the bore 9, indicated in parentheses.

Instead of indentations, it is also possible to use applications of material. Of course, a combination of both types is possible. For the sake of simplicity, only the term indentation will be used in the following. Fig. 3 shows the surface structure 10, which is already in Fig. 1 and 2 is shown. These are interrupted, circumferential radial structures 14. In Fig. 3 nine radial structures 14 are shown, which are axially spaced by a distance c. The radial structure 14 here consists of circumferentially arranged indentations, which are not continuous, but interrupted by structure distances. In other words, indentations and unchanged areas between the indentations alternate in succession. Each indentation of the radial structure 14 has a structure length g, and each distance between the indentations is referred to here as a structure spacing f. In this case, the structure length g and the structure distance f are sheet dimensions, wherein the distance c is a length dimension which runs parallel to the central axis 7e.

The surface structure 10 after Fig. 3a has broken, circumferential axial structures 15. An axial structure 15 in this case comprises indentations which extend in the axial direction, ie parallel to the central axis 7e, and are radially spaced apart. Here, the structure length g and the structure distance f are length measures which are parallel to the central axis 7e. In this case, the (here) radial distance c is a radian measure and is between two radially arranged recesses 2c. In the axial direction successive axial structures 15 are each arranged offset so that an indentation is axially below or above an interruption.

In Fig. 3b the surface structure 10 is shown with a diagonal structure 16. The indentations of the diagonal structure 16 run in the in Fig. 3b shown projection angle at an angle k, which is here, for example, 45 °, but is not limited to this value. In this case, the structure length g and the structure spacing f in the projection plane are length dimensions, a distance of the diagonal structures 16 from one another being indicated as distance c, which here is equal to the distance c of the indentations.

The diagonal structure 16 is also adapted to a rotational movement 11 (see Fig. 2 ) of the piston member 7 to generate about its central axis 7e, whereby a turning of the seal seat in the body 2 by the sealing tip 7c of the piston member 7 is prevented or reduced.

A variation of the diagonal structure 16 in the form of a cross structure 17 shows Fig. 3c , The structure length g of the respective cross-forming indentations is the same here. The cross structure 17 from the diagonal structure 16 after Fig. 3b and composed of a mirrored diagonal structure 16. These two Diagonal structures 16 are arranged under the structural angles k, which are the same size here, but also mirrored.

In Fig. 3d For example, a surface structure 10 in the form of a wave structure 18 is shown. The distances c between the recesses with the respective structure length g and between the wave structures 18 are the same size. A peak-to-peak amplitude of the wave structure 18 is designated by the reference symbol j.

Fig. 3e shows the surface structure 10 with a circular structure 19. The circular structures 19 are arranged axially so that there is always a circle above / below a gap between two circles. An axial distance j indicates the distance between the circular structures 19 with each other. The structure length g is the diameter of a circular indentation and the distance c indicates the distance between the circular indentations in a circular structure 19.

A circular indentation can only consist of a circle or a circular area.

The distances, so the interruptions, between the indentations and the lengths of the indentations can be the same size as shown or even different.

The structure length g may e.g. 0.25 ... 5 mm, wherein for the lengths of the interruptions, i. the distances c, d, e as well as, for example, for f, j 'corresponding Maßbereiche can be used.

Finally shows Fig. 4 schematic enlarged sectional views of surface structures 10 according to the invention in different training variants.

The reference character h denotes a feature width, irrespective of whether it is an axial, radial or diagonal structure. A structure depth i indicates the depth of the indentation of the respective structure.

In the opposite case, the structure depth i is a plot of the respective structure whose height or dimension by which the structure protrudes from the guide surface 7d or bore surface 9a.

The feature width h may be e.g. 0.02 ... 2 mm, wherein the structure depth i may be, for example, 0.1 to 2 times the structure width h. These dimensional examples also apply in the case of corresponding applied surface structures 10.

The various exemplary structural shapes are in an order from top to bottom exemplary cross sections. A rectangular or square structural form W is shown above. Below this there is a V-shaped (pointed / cone-shaped) indentation as structural form X. A structural form Y shows a semicircular / oval indentation, and a structural form Z indicates a combination of all structural forms W, X, Y. Of course, other shapes are possible.

The different surface structures 10 can be used, depending on the type of medium which flows around the piston element 7 or through the bore 9. It is of course also possible that the surface structures 10 are arranged in different combinations or only on partial areas of the guide surface 7d of the piston element 7 or / and the bore surface 9a of the bore 9.

Preferred dimensional ranges for the surface structure 10 may include i.a. also be dependent and in relation to the circumference of the guide portion 7a of the piston member 7 and to the pressure areas in the respective application.

The surface structures 10 are thus suitable for piston element arrangements. In this case, sealing elements, in particular metallic sealing elements, such. Nozzle needles to be provided as piston elements with guide portions 7a of high pressure injectors. Piston elements may be used in pneumatic and hydraulic valves and pressure generators for gases and liquids, i. Fluids of any kind can be used.

In addition, another area of use of the surface structures 10 is on piston element assemblies with pistons and piston guides, as well as e.g. Cylinder walls of pumps, especially high-pressure pumps, and injectors possible.

An introduction or molding of the surface structures 10 in the guide surface 7 d of the guide portion 7 a of the piston member 7 as well as in the bore surface 9 a of the bore 9 can be prepared by suitable, different methods, For example, beam removal methods such as laser, done. For applying the surface structures 10, suitable material application methods are known to the person skilled in the art.

Generation of the various surface structures 10 may, for example, be performed by means of a programmable random generator, parameters such as e.g. Structure length g and distance c (and of course all others) are permanently specified. Of course, it is also possible that the surface structures 10 are predetermined beforehand.

By the embodiments described above, the invention is not limited, but it is modifiable within the scope of the appended claims.

For example, e.g. It is conceivable that the surface structures 10 can also be arranged in combination on the guide surface 7d and on the bore surface 9a both in the same and in different embodiments.

If the surface structure 10 is arranged on the guide section 7a of the piston element 7 and on the bore surface 9a of the bore, these two surface structures 10 may be opposite, axially spaced or overlapping.

LIST OF REFERENCE NUMBERS

1

injection

2

body

3

injector cap

3a

outer surface

3b

surface treatment

4

inlet bore

5

pressure chamber

6

injection chamber

7

piston element

7a

guide section

7b

inlet section

7c

sealing tip

7d

guide surface

7e

central axis

8th

spiracle

9

drilling

9a

bore surface

9b

gap

10

surface structure

11

rotary motion

12

turbulence

13

Longitudinal direction of movement

14

radial structure

15

axial structure

16

diagonal structure

17

cross structure

18

wave structure

19

circular structure

a, b

axial length

c, d, e

distance

f, j '

pattern pitch

G

structure length

H

structure width

i

structure depth

j

wave height

k

structure angle

P ₁ , P ₂

medium pressure

W, X, Y, Z

structural form

Claims (15)

Piston element arrangement, in particular for an injection nozzle for fluids, comprising a piston element (7) with at least one guide section (7a) and a central axis (7e); and a bore (9), in which the at least one guide section (7a) of the piston element (7) is guided longitudinally displaceably,
characterized in that
the piston element assembly has at least one surface structure (10) with a number of axially spaced discontinuous circumferential structures (14 ... 19). Piston element assembly according to claim 1, characterized in that each of the axially spaced discontinuous circumferential structures (14 ... 19) comprises indentations and / or plots which are spaced from interruptions having neither indentations nor plots, the indentations and / or applications and interruptions in a row on the circumference of an imaginary circular plane which is perpendicular to the central axis (7e), are arranged annularly. Piston element arrangement according to claim 2, characterized in that each indentation and / or application of the axially spaced-apart discontinuous, circumferential structures (14 ... 19) has a structure length (g) and the interruption respectively arranged between two indentations has a structure spacing (f) , wherein the structure length (g), the structure distance (f) and an axial distance of the interrupted, circumferential structures (14 ... 19) have the same size or different dimensions. Piston element arrangement according to claim 3, characterized in that the structure length (g) has a dimension in a range of about 0.25 ... 5 mm. Piston element assembly according to claim 3 or 4, characterized in that a structure width (h) of a molding or a plot has a dimension in a range of about 0.02 ... 2 mm. Piston element arrangement according to claim 5, characterized in that a structure depth (i) of a indentation or a height of a plot is about 0.1 to 2 times the structure width (h). Piston element arrangement according to one of claims 2 to 6, characterized in that a cross section of a molding or / and a plot is rectangular, pointed or conical, round or oval, or formed in a combination thereof. Piston element arrangement according to one of the preceding claims, characterized in that the at least one surface structure (10) is produced by means of a beam removal method and / or a material application method, for example by means of scraping, embossing, pressing, coating. Piston element arrangement according to one of the preceding claims, characterized in that the at least one surface structure (10) on the guide portion (7a) of the piston element (7) is arranged. Piston element arrangement according to claim 9, characterized in that the at least one surface structure (10) on the guide portion (7a) of the piston element (7) has a diagonal structure (16) in such a way that a rotational movement of the piston element (7) can be generated when flowing around with a medium , Piston element arrangement according to one of claims 1 to 8, characterized in that the at least one surface structure (10) on a bore surface (9a) of the bore (9) is arranged. Piston element arrangement according to one of claims 1 to 8, characterized in that at least one surface structure (10) on the guide portion (7a) of the piston element (7) is arranged, and that at least one surface structure (10) on a bore surface (9a) of the bore (9a) 9) is arranged. Piston element arrangement according to claim 12, characterized in that the at least one surface structure (10) on the guide portion (7a) of the piston element (7) and the at least one surface structure (10) on a bore surface (9a) of the bore (9) are opposite, axially spaced or overlap. Injection nozzle (1), in particular hole nozzle for an internal combustion engine, with: a. a body (2); b. a piston member assembly comprising a piston member (7) formed as the nozzle needle and a bore (9) in the body (2) in which the piston member (7) is slidably guided; c. a pressure chamber (5) which communicates with an inlet bore (4) and via a passage with a spray chamber, said passage having a sealing seat for cooperation with a sealing tip (7c) of the piston element (7); and d. at least one injection hole (8), via which the injection chamber (6) communicates with the outside of the body (2),
characterized in that e. the piston element arrangement is designed according to one of the preceding claims. Injection nozzle (1) according to claim 14, characterized in that an outer surface (3a) of a nozzle tip (3) of the body (2) has a surface treatment (3b) which as fine polishing with a certain degree of fineness, preferably with a surface roughness of approximately Rt ≤ 1.7, is formed.

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