CN105370445B

CN105370445B - Gas injector with defined microstructure on sealing surface

Info

Publication number: CN105370445B
Application number: CN201510487241.8A
Authority: CN
Inventors: F·耶格勒; T·凯德洛夫斯基; R·哈马达; J·舍费尔; O·奥尔哈费尔
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2014-08-11
Filing date: 2015-08-10
Publication date: 2020-02-18
Anticipated expiration: 2035-08-10
Also published as: CN105370445A; DE102014215870A1

Abstract

The invention relates to a gas injector for injecting gaseous fuel, comprising a valve closing element (2) for opening and closing a flow opening (3) and a valve seat (4) having a second sealing surface (6), wherein the valve closing element (2) has a first sealing surface (5), at least one of which has a microstructure (7) with a defined geometry.

Description

Gas injector with defined microstructure on sealing surface

Technical Field

The invention relates to a gas injector for injecting gaseous fuel, having a sealing surface with a geometrically well-defined microstructure.

Background

Nowadays, gas-driven vehicles, for example with natural gas or hydrogen, are increasingly used. However, unlike liquid fuels, gaseous fuels have different requirements, requiring specially developed injectors. In particular in the case of direct injection of gas, which is injected directly into the combustion chamber, new methods must be used due to the high pressure of the gas and the lack of lubrication. By arranging the gas injector directly at the combustion chamber, for example an elastomeric sealing element cannot be used for sealing due to the high temperature at the combustion chamber. Furthermore, due to the lower density of the gas compared to the liquid fuel, the gas injector in the open state necessarily exposes a large cross section.

Disclosure of Invention

In contrast, the gas injector for injecting gaseous fuel according to the invention having the features of claim 1 has the advantage that an improved tightness can be achieved. Furthermore, the tightness can be achieved over the entire service life of the gas injector. In this case, the sealing is ensured even in the presence of the smallest particles that can be generated, for example, by the output shaft during operation of the gas injector, and the sealing seat cannot be damaged in such a way that it is not negatively impaired in the open state of the gas injector. According to the invention, this can be achieved in that a valve closing element, for example a valve needle, for opening and closing the through-flow opening has a first sealing surface and the valve seat has a second sealing surface which closes the through-flow opening in the closed state of the gas injector. In this case, according to the invention, a microstructure having a defined geometry is provided on at least one sealing surface. The microstructure is formed on the surface of the sealing surface, for example, by providing geometrically defined recesses. Here, the microstructure preferably has a depth of about 10 μm. By providing a defined microstructure, the area in which the sealing surfaces are in effective contact in the closed state of the gas injector is reduced in this way, i.e. a high surface pressure can be achieved without the sealing force having to be increased to the same extent for this purpose. Furthermore, the defined geometry of the microstructure ensures that a very high stability is present against particle wear, which is only difficult to avoid, since a plurality of closed lines between the two sealing partners, which prevent leakage paths in the closed state, are always present via the microstructure between the sealing surfaces.

Preferably, the microstructures are provided on the first sealing surface and the second sealing surface. By providing the microstructure on both sealing partners, a reliable seal can be achieved over the service life of the gas injector.

It is further preferred that the microstructure is formed on an annular closed region on one of the sealing surfaces, preferably on both sealing surfaces.

Preferably, the microstructure on one of the sealing surfaces has a smaller area than the contact surface between the two sealing surfaces in the closed state of the gas injector. In particular, the production costs can therefore be kept relatively low. Alternatively, the microstructure on one of the sealing faces has a larger area than the contact surface between the two sealing faces. In particular, it is therefore possible to increase the contact surface on one of the two sealing partners over the service life, and therefore a reliable seal is always ensured at the contact region of the two sealing partners, since the contact region is always covered by the microstructure of the larger geometry.

Further preferably, at least 50% of the contact surfaces of the sealing surfaces are provided with geometrical microstructures.

Further preferably, the valve seat of the gas injector is a flat seat or a conical seat. The sealing surface of the valve closure element is configured accordingly.

According to a particularly preferred embodiment of the invention, the defined microstructure comprises a plurality of annular recesses (grooves) extending over the sealing surface. The annular recesses are arranged concentrically with respect to one another, and thus a parallel multiple sealing is achieved by a plurality of concentric sealing lines in the flow direction. Preferably, the annular groove is interrupted by a web. This contributes to efficiently suppressing the leak path on the annular recessed portion.

According to an alternative configuration of the invention, the geometric microstructure comprises a plurality of oval or rectangular recesses.

The geometrically defined microstructure is preferably produced by means of a laser. Other geometrical configurations, such as oval, n-cornered or shallow grooves extending in the circumferential direction, are also contemplated.

Further preferably, the valve closing element is an inwardly opening closing element or an outwardly opening closing element. In this case, it is particularly preferred to provide the outwardly opening closing element, since in particular a large cross section can be opened with a small stroke, so that a sufficient amount of gas can be injected in a short injection time.

The invention further relates to an internal combustion engine having a combustion chamber and a gas injector according to the invention, wherein the gas injector is arranged directly on the combustion chamber for direct injection of gaseous fuel.

Drawings

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the drawings:

figure 1 shows a schematic perspective view of a gas injector according to an embodiment of the invention,

figure 2 shows a schematic partial cross-sectional view of figure 1,

figure 3 shows a schematic top view of the geometrically defined microstructure of the sealing surface of figure 1,

figure 4 shows a cross-sectional view of figure 3,

figure 5 shows the view as in figure 3 with defects present in the geometrically defined microstructure,

figure 6 shows a schematic perspective view of a gas injector according to a second embodiment,

figure 7 shows a schematic cross-sectional view of figure 1,

figure 8 shows a schematic perspective view of a gas injector according to a third embodiment of the invention,

fig. 9 and 10 show schematic top views of other different preferred geometrically defined microstructures.

Detailed Description

The gas injector 1 for injecting gaseous fuel directly into the combustion chamber 10 is described in detail below with reference to fig. 1 to 5.

As is illustrated by fig. 1 and 2, the gas injector 1 comprises a valve closing element 2 and a valve seat 4. When the closing element 2 is moved axially as indicated by the double arrow a, the through-flow opening 3 is opened or closed between the closing element 2 and the valve seat 4.

The first sealing surface 5 is arranged on the valve closing element 2. The second sealing surface 6 is formed on the valve seat 4. A geometrically defined microstructure 7 is formed on the first sealing surface 5. The microstructure 7 comprises a plurality of recesses 70, which are produced, for example, by means of a laser. No microstructure is formed on the second sealing surface 6. The sealing surface 6 is produced by conventional surface machining methods, for example grinding or the like.

Geometrically defined microstructures are shown in fig. 3 to 5. As shown in fig. 3, the recesses 70 of the geometrically defined microstructure 7 are substantially elliptical. The individual recesses are each located on a common line L. For better simplicity, only one line L is shown in fig. 3 to 5. The line L is an annular line because the gas injector of the first embodiment is a gas injector having a flat seat (see fig. 1). Here, the plurality of recesses are arranged on a plurality of annular lines L extending concentrically relative to one another. As shown in fig. 3, the recesses 70 on respectively adjacent annular lines are slightly offset in the circumferential direction. The recesses 70 are all of identical design here. However, this need not necessarily be the case, but it is also conceivable for different annular lines L to have different geometrically defined shapes.

Fig. 5 shows, by way of example, the possibility of damage 8 to the microstructure 7 when, during the closing process, particles or the like are located between the two sealing

surfaces

5, 6. Thus, a connection between adjacent recesses 70 may be established, which is illustrated by the double arrow D. In the closed state, however, no connection can occur between the side 11 facing the combustion chamber and the side 12 facing away from the combustion chamber in the flow direction C, since at least one closed sealing line between the two sealing

surfaces

5, 6 is always maintained by a plurality of annular lines with recesses.

As is evident directly from fig. 3 to 5, the effective bearing area between the two sealing surfaces is reduced by the defined surface structuring by means of the microstructure. This does not create an additional leakage path along the flow direction C. Even if the damage 8 is accumulated due to particles or such substances, a leakage path in the flow direction C is not directly formed. By providing a plurality of recesses 70 in a staggered manner along the flow direction C, it is absolutely impossible to create a leakage path over the service life.

Fig. 3 to 5 also show the direct contact area 9 of the first sealing surface 5 and the second sealing surface 6, which is illustrated by dashed

lines

91 and 92. In the first embodiment, the contact region 9 is smaller than the area of the microstructure 7. As a result, possible deformations of the valve seat 4, which may increase in the width direction, can be absorbed in particular with increasing service time by the larger surface area of the microstructure 7.

Fig. 6 and 7 show a gas injector 1 according to a second embodiment of the invention. Unlike the first embodiment, the gas injector 1 of the second embodiment is provided with a conical seat. Here, the contact area 9 of the second embodiment is larger than the area of the microstructure 7. In other respects, the exemplary embodiments correspond to the exemplary embodiments described above, so that reference is made to the description given there.

Fig. 8 shows a gas injector 1 according to a third embodiment of the invention. The third exemplary embodiment corresponds essentially to the second exemplary embodiment, wherein the first sealing surface 5 has an arcuate shape in cross section. The second sealing surface 6 is likewise embodied with a correspondingly curved cross section.

Fig. 9 and 10 show further embodiments according to the invention of a geometrically defined microstructure 7 for a sealing surface. The microstructure 7 shown in fig. 9 is constituted by grooves interrupted in the circumferential direction. Here, an additional web 72 is provided.

Fig. 10 shows a microstructure 7 in which an oval recess 70 is formed. The oval recesses 70 are likewise again arranged on a plurality of parallel sealing lines L.

Thus, according to the invention, the sealing area in effective contact can be reduced by machining a geometrically defined microstructure on at least one of the sealing surfaces of the two sealing partners, so that a high surface pressure between the sealing partners can be achieved without the sealing force required therefore having to be increased to the same extent. Furthermore, it is possible to achieve by means of a special configuration of the microstructure 7, as is schematically shown in fig. 5, that the gas injector according to the invention is extremely robust against wear caused by particles.

Claims

1. A gas injector for injecting gaseous fuel, comprising

A valve closing element (2) for opening and closing a through-flow opening (3),

-wherein the valve closing element (2) has a first sealing surface (5); and

-a valve seat (4) having a second sealing surface (6),

-wherein at least one of the first sealing surface (5) and the second sealing surface (6) has a microstructure (7) with a defined geometry, wherein the microstructure (7) comprises a plurality of geometrically defined recesses (70) which are arranged on a plurality of annular lines (L) extending concentrically with respect to one another and which are offset in the axial direction on respectively adjacent annular lines.

2. A gas injector according to claim 1, characterized in that the microstructure (7) is provided on the first sealing surface (5) and/or the second sealing surface (6).

3. A gas injector according to claim 1 or 2, characterized in that at least 50% of the contact surface between the first sealing surface (5) and the second sealing surface (6) has a microstructure (7) in the closed state of the gas injector.

4. A gas injector according to claim 2, characterized in that the microstructure constitutes an annular closed area on the first sealing surface (5) and/or the second sealing surface (6).

5. A gas injector according to claim 2, characterized in that the microstructure (7) on one of the first sealing surface (5) and the second sealing surface (6) has a smaller area than the contact area (9) between the first sealing surface (5) and the second sealing surface (6).

6. A gas injector according to claim 2, characterized in that the microstructure (7) on one of the first sealing surface (5) and the second sealing surface (6) has a larger surface than the contact surface (9) between the first sealing surface (5) and the second sealing surface (6).

7. A gas injector according to claim 1 or 2, characterized in that the valve seat (4) is a flat seat or a conical seat.

8. A gas injector according to claim 2, characterized in that the microstructure comprises a plurality of grooves extending annularly on the first sealing surface (5) and/or the second sealing surface (6).

9. Gas injector according to claim 8, characterized in that the annular groove is interrupted by a web (72).

10. A gas injector according to claim 1 or 2, characterized in that the microstructure (7) comprises a plurality of oval or rectangular recesses.

11. An internal combustion engine comprising a combustion chamber (10) and a gas injector according to any one of the preceding claims, wherein the gas injector is arranged directly on the combustion chamber.