WO2011032776A1

WO2011032776A1 - Combustion chamber window

Info

Publication number: WO2011032776A1
Application number: PCT/EP2010/061257
Authority: WO
Inventors: Werner Herden; Pascal Woerner; Juergen Raimann
Original assignee: Robert Bosch Gmbh
Priority date: 2009-09-15
Filing date: 2010-08-03
Publication date: 2011-03-24
Also published as: DE102009029479A1

Abstract

The invention relates to a combustion chamber window for transmitting light into or from a combustion chamber (14) of an internal combustion engine (109), for example for use in a laser spark plug (11) that is highly resistant against dirt.

Description

description

title

Combustion chamber window

State of the art

The invention relates to a combustion chamber window according to the preamble of the independent claim and to a method for producing the combustion chamber window. The invention further relates to a laser spark plug and an internal combustion engine with a

combustion chamber window according to the invention.

Such combustion chamber windows are used, for example, for the optical analysis of

Combustion in a combustion chamber of an internal combustion engine is used, on the other hand, such combustion chamber windows are used in the context of laser ignition systems, for example in motor vehicles, in stationary engines or in turbines.

A central problem in connection with the use of

Brennraumfenstern for transmission of light into or out of a combustion chamber of an internal combustion engine is that it comes to operation of the internal combustion engines for deposition of combustion residues, such as oil ash and its main components calcium sulfate and calcium phosphate, on the combustion chamber windows and that these residues the transmission of light through the Lower the combustion chamber window. In the example mentioned use of the combustion chamber window for analyzing the combustion in the combustion chamber thus leads to a falsification of the combustion chamber lighting, in which further exemplified use of the combustion chamber window in the context of a Laserzündsystems it comes through the deposition of combustion residues to a deterioration of the ignition behavior of the internal combustion engine. To solve this problem and to avoid combustion residues on the combustion chamber window has been proposed in the European patent application EP1887218 to introduce the combustion chamber side facing the combustion chamber window laser light whose intensity is outside a specified interval.

A disadvantage of the solution known from the prior art is that the intensity of the light transmitted through the combustion chamber window can no longer be freely selected.

Advantages of the invention

Inventive combustion chamber window according to the features of the independent

Claim, however, have the advantage that pollution of the

Brennraumfensters always and regardless of the intensity of external lighting can be avoided.

The invention is based on the Applicant's finding that a large proportion of the deposits which form on combustion chamber windows during operation of the associated internal combustion engine go back to combustion residues, for example oil pockets. In particular, at high temperatures, this leads to solid adhesions, in particular of

Phosphates and sulfates, on the surface of the combustion chamber window.

Investigations by the Applicant According to the addition of numerous

Combustion residues, for example of sulfates and phosphates, on a previously clean combustion chamber window from the prior art during operation of the associated internal combustion engine in such a way that distributed in a first phase on the combustion chamber window, consisting of the combustion residues

Training deposit germs. It was also observed that, at the same time and following this, first and foremost, it would lead to a growth of this area

Depositing nuclei comes as long as, until substantially all of the combustion chamber exposed surface of the combustion chamber window is covered with a substantially homogeneous layer. As a result of the increasing coverage of the combustion chamber window, the transmission through the combustion chamber window decreases relatively rapidly in this phase,

for example, to 30% of the original transmission within the first 200h

Operating hours of the internal combustion engine. It has further been proven that when on In this way, a substantial coverage of the combustion chamber window is achieved, further deposits of combustion residues barely done in a planar manner, but such that form on the existing layer dendritic-like structures, and grow more deposits on these dendrites in the air. In this phase, the transmission through the combustion chamber window, for example, at a value of 30% of the original transmission, remains largely constant over a long period of operation of the internal combustion engine.

The present invention is based on the idea of already applying a microstructure to the combustion chamber window in the production process, which on the one hand has a

has comparatively high transmission for visible and / or near-infrared light, for example 70%, and which is furthermore such that, starting from it, deposits of combustion residues, for example of sulphates and

Phosphates, primarily not in a flat manner, but in the direction perpendicular to the surface of the combustion chamber window, on the structure. In this way it is achieved that the transmission of the combustion chamber window over a long period of operation of the internal combustion engine is largely constant at a high value.

With combustion chamber windows according to the independent claim 1, long service lives have been realized in piston engines and in turbines, which could be optimized by the measures mentioned in claims 2 to 13.

It has proved to be particularly favorable to apply microstructures on the combustion chamber window from a material which is chemically related to the oil pockets and / or comprises fractions of sulfates or phosphates, in particular sulfate and phosphates, in particular calcium sulfate and / or calcium phosphate.

Rational methods for producing the combustion chamber windows according to the invention are given in the independent method claim.

By optionally provided heating of the applied microstructure in the context of the manufacturing process, its resistance can be improved, for example, its water solubility can be reduced. Here, for example, for structures of calcium sulfate (gypsum) from heating to 300 ° C to 500 ° C a sparingly soluble structure in water, from a heating at 500 ° C to 700 ° C a water-insoluble structure and heating to about 1180 ° C causes a High temperature modification takes place, in which a so-called anhydrite I forms, particularly resistant material.

drawing

Figure 1 shows a schematic representation of an internal combustion engine with a

Laser ignition.

Figure 2a, b, c show schematically inventive combustion chamber window

Description of the embodiment

An internal combustion engine carries in FIG. 1 in its entirety the reference numeral 109. It serves to drive a motor vehicle, not shown, or a stationary motor likewise not shown. The engine 109 includes a plurality of cylinders 129, one of which is shown in FIG. A combustion chamber 14 of the cylinder 129 is bounded by a piston 16. Fuel 229 enters the combustion chamber 14 directly through an injector 18, which is connected to a fuel pressure accumulator 209.

Fuel 229 injected into combustion chamber 14 is ignited by means of a laser pulse 24 which is radiated into the combustion chamber 14 by an ignition device 27 comprising a laser spark plug 11 and focused by means of focusing optics 261. The

Focusing optics 261 projects directly into the combustion chamber 14 and thus simultaneously represents the combustion chamber window 141, the laser spark plug 11 or the internal combustion engine 109, which enables the transmission of light into the combustion chamber 14. The

Laser spark plug 11 is fed by a light source 10 via a light guide 12 with a pumping light. The light source 10 is controlled by a control and regulating device 32, which also controls the injector 18.

In addition to the light-conducting device 12, the light source 10 also includes a diode laser 13, which, in response to a control current, emits a corresponding pump light via the light source 12

Lichtleiteinrichtung 12 outputs to the laser spark plug 11. The laser spark plug 11 comprises, for example, a monolithic passively Q-switched solid state laser (not shown) next to the combustion chamber window.

2a, the combustion chamber window 141 is shown schematically, wherein on one side of the combustion chamber window 141, the side, which is intended for direct contact with fuel gases, microstructures 70 made of calcium sulfate and / or calcium phosphate material are provided. In this example, the structures are arranged like a checkered pattern, that is, the structures consist of discrete square structural elements 71 wherein between the structural elements 71 also square and equal areas are arranged, in which no

Calcium sulfate and / or calcium phosphate-containing material is provided. The side length of the square areas in this example is Ιμηη. The high of

Structural elements is about 250nm. FIGS. 2b and 2c show alternative embodiments of the microstructure 70 in the form of a rectangular grid and in the form of a microstructure 70 with structural elements 71 with a round base. Other geometries of the microstructures 70 and the structural elements 71 are possible. The microstructures 70 or structural elements 71 have feature sizes (e.g., side lengths, diameters, thicknesses of lines, etc.) in the range of 0.3 to 5μηη. Open areas within contiguous microstructures 70 or typical spacings of adjacent structural elements 71 are also of this order of magnitude.

The following are examples of parameters of further microstructures 70 indicated, which were applied to combustion chamber windows 141, with these combustion chamber windows 141 good results were achieved.

In a first further example, one side of a combustion chamber window 141 was provided with a microstructure 70 made of calcium sulfate in a checkered pattern with a microstructure (structure height: 200 nm, microstructured surface: 50%, no calcium sulfate was detectable in the interstices of the structure (height <10 nm)) ,

In the second further example, a part of one side of a combustion chamber window 141 with a microstructure 70 made of calcium phosphate was gridded with a microstructure (structure height: 150 nm, microstructured surface: 25%, no calcium sulfate was detectable in the interstices of the structure (height <10 nm) )). In a third further example, one side of a combustion chamber window 141 has been provided with a microstructure 70 of a mixture containing 50% calcium sulfate and 50% calcium phosphate with a microstructure comprising round structural elements 71. (Structure height: 400nm, surface covered by microstructure: 40%, in the interstices of the structure no material of the microstructure was detectable (height <10nm)).

In a fourth further example, a portion of a side of a combustion chamber window 141 having a microstructure 70 of a mixture containing 50% calcium sulfate and 50% alumina has been provided with a microstructure that is irregular

Structural elements 71 has. (Structure height: 300nm, surface covered by microstructure: 15%, in the interstices of the structure no material of the microstructure was detectable (height <10nm)).

To produce the combustion chamber windows 141 according to the invention, it is provided that a coherent base coating of a liquid phase is first deposited on the combustion chamber window on the combustion chamber window, which consists for example of sapphire or quartz glass. It is envisaged that subsequently,

For example, by means of focused laser radiation, material is selectively removed so that the microstructures 70 remain on the combustion chamber window.

Finally, by heating the microstructure 70 to 300 ° C to 500 ° C and / or to 500 ° C to 700 ° C and / or to above 700 ° C, in particular to above 1180 ° C, the water solubility of the microstructure can be reduced.

Claims

claims

1. combustion chamber window for the transmission of light into or out of a combustion chamber (14) of an internal combustion engine (109), characterized in that at least on a part of the surface of the combustion chamber window (141) microstructures (70) are made of a material, wherein the microstructures (70) have a height of at least 100 nm and not less than 5% and not more than 50% of that part of the

Cover surface of the combustion chamber window (141) and wherein not more than 95% and not less than 50% of the part of the surface of the combustion chamber window (141) the material is at most with a layer thickness of 25nm, in particular at most with a layer thickness of lOnm.

2. combustion chamber window according to claim 1, characterized in that the part of

Surface of the combustion chamber window (141) is a side of the combustion chamber window (141).

3. combustion chamber window according to claim 1 or 2, characterized in that the

Material comprises calcium sulfate and / or calcium phosphate.

4. combustion chamber window according to one of the preceding claims, characterized

in that the material contains at least 90% by weight of calcium sulphate or contains at least 90% by weight of calcium phosphate or that the sum of the proportions of calcium sulphate and calcium phosphate is at least 90%.

5. combustion chamber window according to one of the preceding claims, characterized

characterized in that the microstructures (70) have a height of at least 150 nm, in particular at least 200 nm.

6. combustion chamber window according to one of the preceding claims, characterized

in that the microstructures (70) have a height of at most 100 nm, in particular at most 500 nm.

7. combustion chamber window according to one of the preceding claims, characterized

characterized in that the microstructures (70) have a mean height in the range of 150nm to 100nm, especially in the range of 200nm to 500nm.

8. combustion chamber window according to one of the preceding claims, characterized

characterized in that not more than 95% and not less than 50% of the part of the surface of the combustion chamber window (141) the material of the microstructures (70) is not present, in particular no calcium sulfate and / or calcium phosphate material having.

9. combustion chamber window according to one of the preceding claims, characterized

characterized in that the microstructures are not less than 15% and not more than

Cover 40% of the part of the surface of the combustion chamber window (141) and wherein not more than 85% and not less than 60% of the part of the surface of the

Combustion chamber window (141), the material of the microstructures (70), in particular

Calcium sulfate and / or calcium phosphate having material, at most with a layer thickness of 25nm, in particular at most lOnm, is present or the material of

Microstructures (70) is not present, especially no calcium sulfate and / or

Calcium phosphate material is present.

10. combustion chamber window according to one of the preceding claims, characterized

in that the part of the surface of the combustion chamber window (141) for visible and / or near-infrared light has a transmission in the range of 50% to 95%, in particular has a transmission in the range of 60% to 85%.

11. combustion chamber window according to one of the preceding claims, characterized

characterized in that the microstructure (70) comprises discrete structural elements (71), wherein the structural elements (71) each cover areas of the combustion chamber window whose area in the range between 0.1 μηη ² and 25 μηη ² , in particular in the range between 0.5 μηη ² and 5 μηη ² , is.

12. combustion chamber window according to one of the preceding claims, characterized

in that the microstructure (70) has structural elements (71) with feature sizes in the range from 0.3 μm to 5 μm, in particular in the range from 0.7 μm to 2 μm.

13. combustion chamber window according to claim 3, characterized in that the calcium sulfate and / or calcium phosphate material having in water difficult or not soluble is.

14. laser spark plug (11) or internal combustion engine (109) having a combustion chamber window according to one of the preceding claims.

15. A method for producing a combustion chamber window (141) according to one of claims 1 to 12, characterized by the following steps:

- Separation of a coherent base coating from a liquid phase on the combustion chamber window (141)

- Removing parts of the base coat, in particular by means of laser radiation or by means of an etching process, so that it comes to the formation of the microstructure (70)

16. A method for producing a combustion chamber window (141) according to claim 15,

characterized by heating the microstructure (70) to 300 ° C to 500 ° C and / or to 500 ° C to 700 ° C and / or to above 700 ° C, in particular to above 1180 ° C.