DE102015115320A1 - Adhesive layer for a combustion chamber with a pollutant-reducing active layer - Google Patents

Abstract

An engine and method for the production thereof, wherein at least a partial surface of the combustion chamber surface (1) has at least one active layer (11, 12) applied to an adhesive layer (10) comprising aluminum oxide and nickel, the proportion of aluminum oxide being between 2% and 8% lies.

Description

The invention relates to coated combustion chambers and a method for coating combustion chambers.

The consumption of diesel and gasoline engines has been reduced by 20 to 30% in recent years. This effect was achieved substantially by direct injection of the fuel into the combustion chamber or into the piston recess.

All engines also emit unburned particles, e.g. As fuel droplets, soot particles, unburned lubricating oil particles.

Engines are known from the prior art, which produce particulate matter with particle sizes of 10 to 20 micrometers.

This fine dust is absorbed in particular in the nose and in the bronchi of humans and animals and is removed with the help of cilia.

Modern gasoline engines operate with injection pressures of 100 to 200 bar. Modern diesel engines operate with injection pressures of 1000 to 2000 bar. Fuel particles are generated from the nanometer range to the 1 micron range.

Not all fuel particles burn. Some of the particles produce fine matter, which can penetrate into the smallest alveoli. The higher the injection pressures are set, the higher the proportion of fine dust.

To remedy this situation, special filters and catalytic converters are used for gasoline and diesel engines. Nevertheless, significant amounts of fine dust are released and set according to the development of new emission limits.

Currently, the fine pulp release of modern gasoline engines exceeds the fine pulp release of modern diesel engines.

The object of the invention is to provide a motor which has a comparison with the prior art engines lower emissions of fines and / or requires no expensive filters and catalysts.

The object of the invention is also to provide a method for producing such motors.

In order to achieve this object, a method for the production of engines is proposed, in which at least the cylinder head surface and the entire corresponding valve surface is provided with a special coating that influences the combustion process - in the following, active layer.

Engines known from the prior art usually have metal pistons (aluminum pistons, cast pistons, steel pistons).

By the method according to the invention also existing engine types can be converted. For the method according to the invention, therefore, there are no technical obstacles to direct implementation in older and current engine generations, which allows a quick and easy market introduction.

Motor housings today consist of cast iron or aluminum alloys. The valves are usually made of steel and have a significant share of the combustion chamber surface. The pistons used are primarily aluminum pistons, cast pistons and steel pistons.

Aluminum pistons soften at temperatures above 450 ° C and release heat to the cylinder head. The firing temperature is therefore limited according to the prior art.

Cast iron or steel pistons reach higher temperatures between 550 and 650 ° C and can lead to misfires. They also give off heat to the cylinder wall.

Although a large number of prior art coatings are known to exert an influence on the combustion process, it is often difficult to apply these active layers to a combustion chamber surface in a durable manner.

To solve this problem, an adhesion layer is proposed, which on the one hand "buries" in the combustion chamber surface and on the other hand serves as a primer for the active layer.

According to the invention, the adhesive layer is produced by flame spraying a nickel / aluminum mixture onto the combustion chamber surface.

Preferably, the proportion of aluminum in the mixture is between 2% and 8% and more preferably between 3% and 7% and even more preferably about 5%. The proportion of nickel is preferably more than 90% and more preferably more than 93%, in particular about 95%.

In the flame spraying, temperatures of 3000 ° C are reached by the oxidation of the aluminum. As a result, the adhesive layer "digs" into the combustion chamber surface. The particles of aluminum and nickel preferably have a particle size of between 15 and 45 micrometers. It has been shown that with this granulation a particularly good punctiform adhesion of the adhesive layer to the combustion chamber surface is made possible. In addition, this results in a surface of the adhesive layer, which promotes adhesion of an active layer to the adhesive layer. Furthermore, a layer of such grain is much less corrosive than layers formed from particles having a different grain diameter.

More preferably, a layer thickness of the adhesive layer of 100 to 150 micrometers is applied. One or more active layers are then applied to this adhesive layer.

und weiter bevorzugt zwischen 1 und 3.

auf. According to a preferred embodiment, a thermal insulating layer of zirconium oxide is applied to the adhesive layer. Even more preferably, this layer is not smooth, but has pores with a size of between 0.5 and 10

and more preferably between 1 and 3.

on.

It is also possible for catalytic particles to be introduced into the zirconium oxide layer.

According to a further embodiment, an infrared radiation-reflecting active layer is applied directly to the adhesive layer or to the zirconium oxide layer.

In this case, the reflection effect of the active layer has an efficiency of at least 95%, preferably between 97% and 99% based on the reflection of infrared.

This ensures that in the operating state, the combustion chamber temperature is raised to 650 ° C to 800 ° C in the coating of engines of the prior art.

For this reason, the thermal insulating layer of the entire combustion chamber is preferably provided, which allows the raising of the combustion chamber temperature to over 650 ° C.

Preferably, the active layer has infrared rays reflecting metallic particles.

und weiter bevorzugt zwischen 1 und 3.

auf. According to a further embodiment, the active layer or preferably all the active layers have a porosity with pore sizes between 0.5 and 10

and more preferably between 1 and 3.

on.

Due to the high intensity of the infrared radiation, the high temperature and the specified porosity of the combustion chamber surface, complete evaporation and combustion are achieved. Any resulting soot particles are burned with.

It has also been found that the active layers with the specified roughness and porosity are less brittle than smooth surfaces. From the prior art, the positive effect in porosity in the specified range is not known. In the prior art mostly small grain sizes were preferred. Therefore, the positive effect was particularly surprising.

In particular, in the embodiment in which a zirconium oxide layer is applied as an active layer on the adhesive layer, it has been found that the insensitivity of such a coated combustion chamber or engine is particularly well suited for water injection. In particular, when the pores are selected as described above.

As a result of the described embodiment of the combustion chamber with a zirconium oxide layer as the active layer on the adhesion layer, it has been found that fuel and / or water injection can take place after the dead center of the piston and is nevertheless associated with a considerable increase in performance. Preferably, the engine control, in particular the map optimization is adapted to the conditions of use.

For the purposes of the invention, the term combustion chamber surface is understood to mean the cylinder head surface, the valve surface, the land land and the piston surface.

The object of the invention is also achieved with an engine according to claim 8, wherein the entire combustion chamber of the engine or at least a part thereof is coated with at least one adhesive layer on which at least one active layer is arranged.

Preferably, an infrared radiation at least 95% reflective layer is applied to the adhesive layer and / or a zirconium oxide layer is applied.

If an infrared ray reflecting layer is applied, preferably infrared rays are reflected to over 97%.

The infrared-reflective active layer preferably contains inter alia zirconium oxide which has thermally insulating properties and, according to various embodiments, particles of Al 2 O 3-TiO 2, NiAl, Fe, Fe 2 O 3, MgO, ThO 2, tantalum oxide or combinations thereof, preferably with a total weight fraction of 1 to 10 wt Percent contains.

In principle, all particles can be used which have catalyzing properties, especially those which contain aluminum oxides, titanium oxides, carbons or carbides.

Zirconia is not only very thermally stable but also has a low thermal conductivity. The insulating coating preferably has a thermal resistance of less than 5 W / mK and, in one embodiment, is applied to more than 50% of the combustion chamber surface area. According to a preferred process, the coating is carried out by means of plasma spraying or by means of the PLD process. But other, known from the prior art methods are applicable.

und bevorzugt zwischen 1 und 3.

According to a preferred embodiment, the pores of the heat-reflecting layer and / or the zirconium oxide layer have dimensions between 0.5 and 10

and preferably between 1 and 3.

In these areas, a sufficient strength of the active layers is maintained even for long periods of operation of the engine.

In addition, if particles are introduced into the active layers, there is a particularly good penetration of the gas particles and decomposition with the aid of the catalytically active particles which may be present in the active layer.

Further details of the invention will become apparent from the drawings with reference to the description.

In this case, the feature combinations disclosed in the described embodiments should not limit the invention, but also the features of the different embodiments are combined. In the drawings show

1 shows a piston with modified combustion chamber surface,

2 shows a schematic representation of the layer structure for the combustion chamber surface.

LIST OF REFERENCE NUMBERS

1

 Combustion chamber surface

10

Adhesion-promoting and thermally decoupling layer

11

Active layer as insulation layer

12

Active layer with infrared reflection

13

pore

14

Infrared reflecting particles

1 shows a piston 20 whose surface 12 Part of the combustion chamber surface 1 is. The piston 20 points in total 3 Layers on, with the surface layer 12 Infrared rays reflected at over 95%. To the material of the piston 20 Adjacent there is an adhesion-promoting and thermally decoupling layer 10 which is designed to be particularly good and durable on the surface of the base material of the piston 20 can adhere. The adhesive layer has a thickness of 100 to 150 microns and is formed from 95% nickel and 5% alumina, which was applied with flame spraying at 3000 ° C to the combustion chamber surface.

The nickel and aluminum particles had a grain size of 140 microns prior to flame spraying. Due to the oxidation of the aluminum, the aluminum oxide "burns" into the surface of the piston.

Between the infrared ray reflecting layer 12 and the adhesive layer and thermally decoupling layer 10 is an insulating layer of zirconia 11 arranged.

2 shows the schematic layer structure of the combustion chamber surface 1 the combustion chamber coating according to the invention. The stratifications 10 . 11 . 12 have a thickness of 100 microns

The infrared ray reflecting active layer 12 has pores according to this embodiment 13 on, which is an enlargement of the combustion chamber surface 1 causes and leads to evaporation of the combustible components. In addition, the active layer contains infrared-reflecting particles 14 , Overall, the active layer reflects 12 Infrared rays to 96%.

Claims (12)

Process for the production of engines with reduced particulate emissions, the combustion chamber surface ( 1 ) of an engine at least partially with an active layer ( 12 ), characterized by the steps of: - applying an adhesive layer ( 10 ) on at least a part of the combustion chamber surface, wherein the Adhesive layer ( 10 ) is produced by flame spraying an aluminum-nickel mixture, - applying an active layer ( 11 . 12 ) on the adhesive layer ( 10 ). Process for the production of engines with reduced particulate matter, according to claim 1, characterized in that the coating ( 12 ) Pores ( 13 ) with increased compared to conventional metallic combustion chamber surfaces dimensions. Process for the production of engines with reduced particulate matter emission according to one of claims 1 or 2, characterized in that the active layer ( 12 ) Infrared radiation at least 95% reflected. Process for the production of engines with reduced particulate matter emission according to one of claims 1 to 3, characterized in that the infrared radiation reflecting active layer ( 12 ) on an insulating zirconium oxide layer ( 11 ) is applied, which in turn on the adhesive layer ( 10 ) is applied. Process for the production of engines with reduced particulate matter emission according to one of the preceding claims, characterized in that the proportion of aluminum in the mixture for the production of the adhesive layer ( 10 ) is between 2% and 8%. Process for the production of engines with reduced particulate matter emission according to one of the preceding claims, characterized in that the particles for producing the adhesive layer ( 10 ) have a particle size of between 15 and 45 microns. Process for the production of engines with reduced particulate emissions according to one of the preceding claims, characterized in that the infrared radiation-reflecting coating ( 12 ) Metal particles ( 14 ) that reflect infrared rays. Motor with reduced particulate matter emission, which at least in a partial region of the combustion chamber surface ( 1 ) with an active layer ( 11 . 12 ), characterized in that the active layer ( 11 . 12 ) to an adhesive layer ( 10 ), which comprises aluminum oxide and nickel, wherein the proportion of aluminum oxide is between 2% and 8%. Motor with reduced particulate emissions according to claim 8, characterized in that the active layer ( 12 ) Infrared radiation at least 95% reflected. Motor with reduced particulate matter emission according to claim 8 or 9, characterized in that the at least one active layer ( 11 . 12 ) one over conventional metallic combustion chamber surfaces ( 1 ) enlarged dimension of the pores ( 13 ) having. Motor with reduced particulate emissions according to one of claims 8 to 10, characterized in that the active layer ( 12 ) Infrared radiation reflecting metal particles ( 14 ) having. Piston ( 20 ) for an engine according to claim 8, wherein the piston ( 20 ) at least on one subregion at least one active layer ( 11 . 12 ), which is based on an adhesive layer ( 10 ), which comprises aluminum oxide and nickel, wherein the proportion of aluminum oxide is between 2% and 8%.

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