DE102013211681A1 - Fuel injection valve and device for thermal spray coating - Google Patents

Abstract

A fuel injection valve (1), which serves in particular as an injector for fuel injection systems of air-compressing, self-igniting internal combustion engines, comprises a nozzle body (2) and a nozzle needle (3), which is arranged at least in sections in the nozzle body (2). A temperature-resistant layer (20) is provided on an outside (21) of the nozzle body (2). The layer (20) has inner structures (23) made of a material with low thermal conductivity.

Description

State of the art

The invention relates to a fuel injection valve, in particular an injector for fuel injection systems of internal combustion engines, and a device for thermal spray coating. Specifically, the invention relates to the field of injectors for fuel injection systems of air-compression, self-igniting internal combustion engines and the design of temperature-resistant layers of such injectors.

From the DE 100 02 366 A1 is a heat resistant fuel injector for an internal combustion engine known. The known fuel injection nozzle has a nozzle body with a shaft bore, wherein at the combustion chamber end of the nozzle body, a tip region is formed. Furthermore, the nozzle body has at least one injection hole channel, which is introduced into the tip region, wherein the injection hole channel connects the shaft bore with a combustion chamber of the internal combustion engine. Further, a nozzle needle is provided, which is arranged axially displaceable in the shaft bore of the nozzle body, wherein a tip of the nozzle needle is pressed in a rest position upstream of the injection hole channel against a region in the nozzle tip. The tip region of the nozzle body which extends into the combustion chamber of the internal combustion engine is coated on its outside with a temperature-resistant layer, preferably for temperatures above 300 ° C., at least in the area of the sealing seat of the nozzle needle in the shaft bore. The temperature-resistant layer is made of a material having a low thermal conductivity. Metallic or ceramic laminates, in particular tungsten carbide, are particularly suitable as layer material. The heat-insulating layer can also be formed porous because micro-cavities provide for poor heat conduction.

The from the DE 100 02 366 A1 known fuel injection nozzle has the disadvantage that for a sufficient resistance and for the function to be achieved, the reduction of the heat transfer from the combustion chamber to the nozzle body, a large thickness of the temperature-resistant layer is required. Furthermore, the strength of the layer is reduced by micro-cavities. The possible field of application of the known temperature-resistant layer is therefore limited.

From the EP 2 006 410 A2 are known thermal sprayed, gas-tight protective layers for metallic substrates. Here, the spray powder comprises at least two components, of which the first is a silicate mineral or rock and the second is a metal powder and / or another silicate mineral or rock. The proportion of silicate mineral or rock in the spray powder in this case has an alkali content of less than 6 weight percent. Further, it is believed that known ceramic layers such as diamond-like carbon (DLC) and others made by PVD / CVD methods have low coefficients of thermal expansion and therefore can not be operated at high temperatures.

Disclosure of the invention

The fuel injection valve according to the invention with the features of claim 1 and the device according to the invention with the features of claim 9 have the advantage that an improved embodiment of the temperature-resistant layer is made possible. Specifically, a maximum temperature prevailing in the seat portion of the nozzle body at the same time the smallest possible thickness of the temperature-resistant layer, which serves as a thermal insulation layer, are lowered.

The measures listed in the dependent claims advantageous refinements of the fuel injection valve specified in claim 1 or the device specified in claim 9 are possible.

Due to the internal structures, the temperature-resistant layer can be designed with a significantly reduced thermal conductivity, wherein at the same time a high mechanical strength of the layer and due to the reduced temperature good tribological properties can be achieved at the sealing seat. The layer can be made comparatively thin while ensuring thermal protection. Thus, the layer may be provided on the nozzle body of the fuel injection valve. As a result, an effective protection of the nozzle needle is possible. In particular, the layer may be based on YSZ, a quartz glass or a ceramic, the layer having the inner structures of the material with low thermal conductivity. The coating can be carried out under atmospheric pressure, which simplifies the production compared to methods such as PVD and CVD.

In this case, it is particularly advantageous that a sealing seat is formed between the nozzle needle and a valve seat surface configured on the nozzle body and that the layer there at least partially at the tip of the nozzle body and / or at least partially at a nozzle shaft of the nozzle body, which is at the tip of the nozzle body Düsenkörpers extends, is provided. As a result, for example, even when using the fuel injection valve in applications in which the nozzle needle for long periods and permanently in closed state, a protection of the nozzle needle feasible. This is particularly important for engine braking operation in commercial vehicles, since here the nozzle needle is almost permanently in the closed state and thus a particularly high heat input occurs as a result of lack of cooling fuel injections over the duration of the engine braking operation. By the temperature-resistant layer, in this case an effective protection of the sealing seat on the nozzle needle against the high temperatures occurring can be achieved.

The outside of the nozzle body may have edges in the region of the layer, which are preferably designed as rounded edges.

It is also advantageous that the layer has at least one adhesion layer, a main layer and a cover layer, that the main layer is provided between the adhesion layer and the cover layer and that the inner structures are provided at least in the main layer. By the adhesive layer improved adhesion to the substrate, in particular the metallic material of the nozzle body, is possible. Through the main layer, the main properties of the thermal protection layer, in particular on the coating volume, including the additional, the heat conduction degrading internal structures can be realized. About the top layer, the surface of the layer can be completed, which improves, for example, the corrosion protection.

In this case, it is also advantageous that the adhesive layer and the main layer merge into one another in an overlapping region and that the inner structures in the overlapping region in which the adhesive layer and the main layer merge with one another are provided with a smaller average volume fraction than in the main layer. As a result, the inner layer adhesion can be improved as a result of the overlapping of the individual coating phases, which can be achieved, for example, via separate feed channels. Accordingly, it is advantageous that the cover layer and the main layer merge into one another in an overlapping area and that the inner structures in the overlapping area in which the cover layer and the main layer merge with one another are provided with a smaller average volume fraction than in the main layer. Advantageously, the material of which the internal structures are formed is an airgel. Aerogels are highly porous solids in which the volume is largely composed of pores. An airgel may be formed, for example, silicate-based or carbon-based. Aerogels are usually designed in the form of a strongly dendritic structure in which there is a branching of particle chains with very many spaces in the form of open pores. The particle chains in this case have contact points, so that there is an embodiment in the form of a stable, sponge-like network. The pore size of the open pores may be in the nanometer range.

Since the inner structures preferably have no direct contact with the environment, which can be achieved, for example, via the cover layer, inter alia, no air moisture or the like can penetrate into the airgel, which prevents possible cracking from the outset. Furthermore, this also prevents picking up of other substances in the gaseous or liquid state.

It is also advantageous that the internal structures are formed by particles introduced into the material feed during a thermal spray coating process from the material with the low thermal conductivity. In the case of the thermal spray coating process, the volume fraction of the internal structures in the layer can be adjusted via the metering effected during the material supply and optionally also varied with the layer growth.

It is advantageous that the device for thermal spray coating is designed so that the screw conveyor encloses a longitudinal channel, through which the gas flow to the gas outlet can be guided. In a modified embodiment, it is advantageous that the screw conveyor within a longitudinal channel with annular gap-shaped guide cross section, through which the gas flow to the gas outlet can be guided, is arranged. Thus, compact embodiments are possible in which behind the gas outlet one or more nozzles for supplying one or more coating materials are arranged and at the same time continuously or variably the material with low thermal conductivity can be supplied via the screw conveyor. Thus, the temperature-resistant layer can be configured with the internal structures in an advantageous manner.

By virtue of the internal structures in the layer serving as the thermal insulation layer, higher temperatures in the combustion chamber can be permitted, inter alia with respect to the thermal load of a DLC coating of the nozzle needle, by forming the inner structures of the material with low thermal conductivity in the insulation layer so that the temperature range on the DLC coating of the nozzle needle shifts downward. Thus, the thermal load on the nozzle needle is reduced for a specific application or temperature in the combustion chamber by the thermally insulating layer on the outside of the nozzle body. On the other hand, this allows with respect to a certain load capacity of the nozzle needle, in particular a DLC coating of the nozzle needle, an increase in the range of use, in particular higher temperatures in the combustion chamber.

In this case, the adhesion of the DLC coating to the metallic material of the nozzle needle with respect to higher ambient temperatures can be improved.

Brief description of the drawings

Preferred embodiments of the invention are explained in more detail in the following description with reference to the accompanying drawings, in which corresponding elements are provided with identical reference numerals. Show it:

1 a fuel injection valve in an excerpt, schematic sectional view according to an embodiment of the invention;

2 a layer on a substrate in a partial, schematic sectional view according to a possible embodiment of the invention;

3 a device for thermal spray coating in a partial, schematic sectional view according to a first embodiment of the invention;

4 the in 3 with IV designated section of the device in a detailed representation according to the first embodiment of the invention and

5 the in 4 illustrated section of the device according to a second embodiment of the invention.

Embodiments of the invention

1 shows a first embodiment of a fuel injection valve 1 in a partial, schematic sectional view. The fuel injector 1 can be used in particular as an injector for fuel injection systems of air-compressing, self-igniting internal combustion engines. A preferred use of the fuel injection valve 1 consists of a fuel injection system with a common rail, the diesel fuel under high pressure to several fuel injection valves 1 leads. The fuel injection valve according to the invention 1 However, it is also suitable for other applications.

The fuel injector 1 has a nozzle body 2 and a nozzle needle 3 on that in the nozzle body 2 arranged and along an axis 4 is guided. Further, an actuator 5 provided, for at least indirect actuation of the nozzle needle 3 serves as indicated by the double arrow 6 is illustrated.

The nozzle body 2 has a dome 7 and a nozzle shaft 8th on. Further, on the nozzle body 2 an internal valve seat surface 9 designed. Between a valve closing body 10 the nozzle needle 3 and the valve seat surface 9 is a sealing seat 11 educated. With the sealing seat open 11 can fuel from a fuel room 12 that inside the nozzle body 2 is configured, over the open sealing seat 11 to spray holes 13 . 14 be guided to the fuel through these spray holes 13 . 14 to inject into a combustion chamber of an internal combustion engine. By closing the sealing seat 11 this injection is finished. The fuel injector 1 has a temperature resistant layer 20 on, on an outside 21 of the nozzle body 2 is provided. In this embodiment, the layer is 20 partly on the nozzle shaft 8th and partly at the top 7 intended. The nozzle shaft 8th extends to the dome 7 , Special is the layer 20 in one on the outside 21 of the nozzle body 2 intended area 22 , the seal seat 11 on the inner valve seat surface 9 is assigned provided.

The nozzle needle 3 can be suitably coated. Specifically, the valve closing body 10 the nozzle needle 3 be coated. For coating the nozzle needle 3 In particular, a diamond-like carbon coating can be used. However, the temperature resistance of such a wear protection layer on the nozzle needle 3 limited. Through the layer 20 can reduce the thermal load on the coated nozzle needle 3 be shifted to a physically and tribologically easily controllable temperature range. Thus, a significant reduction of the maximum temperatures occurring in the region of the sealing seat 11 on the nozzle body 2 at the same time as small as possible thickness of the layer 20 be achieved. Due to a small thickness of the layer 20 Among other things, the limited space can be taken into account.

2 shows the layer 20 on a substrate 2 ' in a partial, schematic sectional view corresponding to a possible embodiment of the invention. At the substrate 2 ' in particular, it may be the nozzle body 2 act. The layer 20 has a variety of internal structures 23 on top of the layer 20 are distributed. To simplify the representation here is one of the internal structures 23 characterized. In this Embodiment are the internal structures 23 as particulate units 23 in the layer 20 distributed. The internal structures 23 are made of a material with low thermal conductivity. As such a material in particular an airgel in question. The internal structures 23 can be used as airgel particles 23 be designed.

In this embodiment, the layer 20 an adhesive layer 24 , a main layer 25 and a cover layer 26 on. The adhesive layer 24 is directly on the outside 21 of the substrate 2 ' applied. The adhesive layer 24 serves as a bonding agent. On the adhesive layer 24 is the main layer 25 applied. On the main layer 25 is again the top layer 26 applied. The internal structures 23 are at least in the main layer 25 intended. In this embodiment, the internal structures 23 but also in the adhesive layer 24 and in the topcoat 26 intended. Here is a volume fraction of the internal structures 23 and thus an average volume fraction of the internal structures 23 in the main layer 25 each larger than in the adhesive layer 24 and the topcoat 26 ,

In a modified embodiment, an overlap region can also be used 27 and / or an overlap area 28 be provided. This is where the adhesive layer goes 24 and the main layer 25 in the overlap area 27 into each other, with the internal structures 23 in the overlap area 27 are provided with a smaller average volume fraction than in the main layer 25 , Accordingly, the top layer go 26 and the main layer 25 in the overlap area 28 into each other, with the internal structures 23 in the overlap area 28 are provided with a smaller average volume fraction than in the main layer 25 , Here, for the adhesive layer 24 , the main layer 25 and the topcoat 26 different materials are used, wherein in the overlapping areas 27 . 28 a mixture of the materials used in each case is possible. As a result, the inner layer adhesion due to the overlap areas 27 . 28 executed overlap of the individual coating phases can be improved.

3 shows a device 30 for thermal spray coating of a substrate 2 ' in a partial, schematic sectional view according to a first embodiment. At the substrate 2 ' in particular, it may be the nozzle body 2 act. However, the device is suitable 30 also for coating other substrates 2 ' , In particular, a pipe which is intended to ensure thermal insulation from the environment can be provided with a layer on the outside 20 be coated.

The device 30 has a facility 31 with a gas outlet 32 on. The design of the device 31 according to the first embodiment is based on the 4 described in detail. Furthermore, the device 30 jet 33 . 34 . 35 on, about the different materials in an area of a flame 36 can be supplied. The flame 36 This is behind the gas outlet 32 formed by the ignited gas. Preferably, the supply of the material via the nozzles 33 . 34 . 35 in places that are in an area 37 lie. At the area 37 it can also be a level 37 act.

The material with the low thermal conductivity, in particular the airgel, can in principle in the flow direction 38 also looks behind the gas outlet 32 be introduced into the gas and particle flow. However, in this embodiment, the airgel does not become between the gas outlet 32 and the substrate 2 ' but in the flow direction 38 considered before the gas leakage 32 introduced into the gas stream.

The nozzle 33 For example, the material for the adhesive layer 24 respectively. The nozzle 34 can the material for the main layer 25 and the nozzle 35 can the material for the top layer 26 respectively. By suitable timing, the materials can be supplied in chronological succession and optionally also with certain overlap times.

4 shows the in 3 with IV designated section of the device 30 in a detailed representation according to the first embodiment of the invention. The device 31 has a housing 39 on, which is designed in sections tubular and to the gas outlet 32 rejuvenated. In the case 39 is a guide tube 40 arranged in which a longitudinal channel 41 is trained. Through the longitudinal channel 41 the gas becomes the gas outlet 32 guided. Between the guide tube 40 and the housing 39 is a screw conveyor 42 arranged. About the speed of the screw conveyor 42 The material with the low thermal conductivity, in particular the airgel, regardless of the other material supply channels, via the nozzles 33 . 34 . 35 realized are added with the desired proportion. Thus, the aerosol can also be continuously varied so that any continuous intrinsic structural gradient in the layer 20 is feasible.

Thus, the material supply of the airgel, in particular the airgel particles, via a coaxial with the longitudinal channel 41 arranged and from the longitudinal channel 41 separate feed channel through the auger 42 is realized. The gas serves here as transport and fuel gas, the airgel particles to the gas 32 entraining.

About the frequency of the screw conveyor 42 For example, the particle feed, in particular the feed rate of airgel particles, can be used to spray the substrate 2 ' and thus the composition of the individual coating phases are controlled. This can also be used to adjust the thermal expansion coefficient of the layer 20 on the thermal expansion coefficient of the substrate 2 ' be exploited.

Another advantage of through the device 30 realized spray source with the screw conveyor 42 is that the respective base materials of the individual phases of the layer 20 can be supplied via several channels and thus not cumbersome and alternating only over a single channel. This aspect is particularly useful in applications where there are many and, if desired, small substrates to be coated 2 ' meaning.

In addition, there is the advantage that the mixing ratio can be varied as desired. Opposite a prepared mix, in which the internal structures 23 are added to the starting material for coating, thus resulting in the possibility of the proportion of internal structures 23 to vary over the layer structure.

Compared to an embodiment in which a further nozzle after the nozzles 33 . 34 . 35 in front of the substrate 2 ' is provided to meter the airgel, there is the advantage that no undesirable coating of this further nozzle occurs.

5 shows the in 4 illustrated section of the device 30 according to a second embodiment of the invention. In this embodiment, the longitudinal channel 41 configured with an annular gap-shaped guide cross-section. Through the longitudinal channel 41 the gas flow becomes the gas outlet 32 guided. Furthermore, the screw conveyor 42 in this embodiment, within the longitudinal channel 41 arranged. Specifically, a guide tube 40 be provided within the housing 39 is arranged. The gas is then between the housing 39 and the guide tube 40 in the flow direction 38 guided. Inside the guide tube 40 the airgel particles become the gas outlet 32 promoted. In this case, the airgel particles in the flow direction 38 Consider the gas flow before the gas outlet 32 fed.

Thus, about the screw conveyor 42 the material with the low thermal conductivity in the flow direction 38 the gas flow seen before the gas outlet 32 be conveyed into the gas stream.

The base materials for the layer 20 , in particular the adhesive layer 24 , the main layer 25 and the topcoat 26 , can be based on ceramic substances. This is a structural stability of the layer 20 ensured by the base material. In this case, a low thermal conductivity is already achieved. The material with the low thermal conductivity again has a lower thermal conductivity than the base material. Thus obstruct the internal structures 23 the heat conduction in the layer 20 strong. In order to significantly lower the already reduced thermal conductivity of the base material or the base materials, it is thus advantageous that these internal structures 23 be formed in the form of introduced into the coating materials with only very low thermal conductivity. Specifically, the internal structures 23 consist of airgel particles passing through the screw conveyor 42 in the the substrate 2 ' coating spray stream are introduced.

The dimensions of the airgel particles can range from a few micrometers to a few tenths of a millimeter. As base material for the layer 20 For example, a quartz glass and / or partially stabilized zirconium oxide (YSZ) as well as mixtures of quartz glass and YSZ can be used. As part of the layer structure, it is also possible that only over part of the layer 20 internal structures 23 are designed as it is based on the 2 is described.

Using the device 30 produced layers 20 can be formed with appropriate layer thicknesses in relation to the particular application.

Thus, the internal structures 23 be formed by the introduced during the thermal spray coating process in the material supply particles of the material with the low thermal conductivity. The internal structures 23 However, they can also be configured in other ways or in other forms.

The invention is not limited to the described embodiments.

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 10002366 A1 [0002, 0003]
• EP 2006410 A2 [0004]

Claims (11)

Fuel Injector ( 1 ), in particular injector for fuel injection systems of air-compressing, self-igniting internal combustion engines, with a nozzle body ( 2 ) and a nozzle needle ( 3 ), which at least partially in the nozzle body ( 2 ), wherein a temperature-resistant layer ( 20 ) on an outside ( 21 ) of the nozzle body ( 2 ), characterized in that the layer ( 20 ) internal structures ( 23 ) formed of a material of low thermal conductivity. Fuel injection valve according to claim 1, characterized in that between the nozzle needle ( 3 ) and one on the nozzle body ( 2 ) designed inboard valve seat surface ( 9 ) a sealing seat ( 11 ) and that the layer ( 20 ) at least in one on the outside ( 21 ) of the nozzle body ( 2 ) ( 22 ), the sealing seat ( 11 ) on the inner valve seat surface ( 9 ) is provided, and / or that the layer ( 20 ) at least partially on a dome ( 7 ) of the nozzle body ( 2 ) and / or at least partially on a nozzle shaft ( 8th ) of the nozzle body ( 2 ), which leads to the dome ( 7 ) of the nozzle body ( 2 ), is provided. Fuel injection valve according to claim 1 or 2, characterized in that the layer ( 20 ) at least one adhesive layer ( 24 ), a main layer ( 25 ) and a cover layer ( 26 ), that the main layer ( 25 ) between the adhesive layer ( 24 ) and the cover layer ( 26 ) and that the internal structures ( 23 ) at least in the main layer ( 25 ) are provided. Fuel injection valve according to claim 3, characterized in that the adhesive layer ( 24 ) and the main layer ( 25 ) in an overlapping area ( 27 ) and that the internal structures ( 23 ) in the overlapping area ( 27 ), in which the adhesive layer ( 24 ) and the main layer ( 25 ) are intertwined with a smaller average volume fraction than in the main layer ( 25 ). Fuel injection valve according to claim 3 or 4, characterized in that the cover layer ( 26 ) and the main layer ( 25 ) in an overlapping area ( 28 ) and that the internal structures ( 23 ) in the overlapping area ( 28 ), in which the top layer ( 26 ) and the main layer ( 25 ) are intertwined with a smaller average volume fraction than in the main layer ( 25 ). Fuel injection valve according to one of claims 1 to 5, characterized in that the material from which the internal structures ( 23 ) is an airgel. Fuel injection valve according to one of Claims 1 to 6, characterized in that the internal structures are in the form of particulate units ( 23 ) in the layer ( 20 ) are distributed. Fuel injection valve according to one of claims 1 to 7, characterized in that the internal structures ( 23 ) are formed by introduced during a thermal spray coating process in the material supply particles of the material with the low thermal conductivity. Contraption ( 30 ) for thermal spray coating with a gas outlet ( 32 ), at least one nozzle ( 33 . 34 . 35 ), via which at least one material in a flow direction ( 38 ) of a gas flow behind the gas outlet ( 32 ) is feasible in the gas stream, and a screw conveyor ( 42 ), whereby via the screw conveyor ( 42 ) a material in the flow direction ( 38 ) of the gas stream seen before the gas outlet ( 32 ) is conveyed into the gas stream. Apparatus according to claim 9, characterized in that the screw conveyor ( 42 ) a longitudinal channel ( 41 ), through which the gas flow to the gas outlet ( 32 ) is feasible, encloses. Apparatus according to claim 9, characterized in that the screw conveyor ( 42 ) within a longitudinal channel ( 41 ) with an annular gap-shaped guide cross section through which the gas flow to the gas outlet ( 32 ) Is arranged, is arranged.

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