DE202010009040U1 - High pressure discharge lamp - Google Patents

Abstract

High-pressure discharge lamp with a discharge vessel, which contains a filling and electrodes, wherein the discharge vessel is made of quartz glass and wherein the discharge vessel is provided with a layer of a metal oxide, characterized in that the layer of Al 2 O 3 alone or in mixtures containing predominantly Al 2 O 3, is manufactured and translucent and completely covers the light-emitting area of the discharge vessel.

Description

Technical area

The The invention is based on a high pressure discharge lamp according to the Preamble of claim 1. The piston can in particular the discharge vessel of a Be high pressure discharge lamp. It can also be the outer bulb Act such a lamp. These are in particular metal halide lamps, high pressure sodium lamps or high pressure mercury lamps.

State of the art

From the US Pat. No. 5,003,214 For example, a lamp is known in which a reflective layer is applied to the bulb of a high-pressure discharge lamp. The process is based on the preparation of a suspension or paste. A similar procedure is off US Pat. No. 4,012,655 known. Here it is attempted to apply the thickest possible, the piston partially covering layer, for which purpose a special adhesion layer must be applied.

From the GB-A 1 375 081 a coating is known, which consists partly of Al2O3 and is up to 50 microns thick and can be applied in principle by flame spraying.

adversely On the one hand, the multiplicity of method steps is involved in these methods. On the other hand shows that the adhesion of the layer is not fully satisfactory is and that the layer thickness is subject to large fluctuations is.

Presentation of the invention

It The object of the present invention is a high-pressure discharge lamp according to the preamble of claim 1, which is easy and inexpensive to produce and also provides better adhesion and allows high color rendering.

These The object is achieved by the characterizing features of claim 1 solved. Particularly advantageous embodiments can be found in the dependent claims.

The Invention allows the application of thermally insulating and possibly simultaneously reflective coatings on the outside from lamp bulbs. For the production of heat-insulating Coatings according to the principle of thermal conductivity Ceramic particles must be applied to the lamp envelope become. Depending on the design and purpose of the lamp caused by the coating insulating areas on the lamp envelope.

So far the application of the particles was realized by means of a suspension. These suspensions or pastes on the one hand by the solids strong abrasive properties. Furthermore, they tend to clump, since binders and thickeners, so-called thixotropic agents, contain have to be. In addition, in the pastes are different Contain solvents or chemicals. The Coating is done so far by atomizing the paste and spraying done, or by immersion of the lamp bulb, overflow or brushing. After application, the coating must be under considerable heat influence be dried and baked. Through the different ingredients in the pastes, depending on the combination of materials, one more or less achieved good Ansintern the coating on the lamp envelope. adversely In these procedures are the environmental and workloads through the chemicals and solvents that correspond accordingly high energy demand and the sometimes low quality of the Coating with regard to adhesion and surface quality. In addition, the service life of various machine components is due the abrasion by the particles short.

By the novel application of modified thermal flame spraying In the construction of the lamp thermal insulation coatings can be applied directly in the powdery state. The Particles required as a powder without the addition of other chemicals or organic compounds through the thermal Spraying or flame spraying melted onto the glass surface.

For this is a selection of special powders based on Al ₂ O ₃ , pure or mixtures of Al ₂ O ₃ with MgO, ZrO 2, also with doping and / or stabilization by other inorganic materials, for example Y ₂ O ₃ , HfO ₂ , SiO ₂ , TiO 2 or SO 3 , suitable. Here, the share of Al2O3 as a major intermediary However, the heat accumulation effect always be at least 50 wt .-%. By selecting the appropriate powder mixture, the required lighting parameters can be set. An 8% level of Y2O3 or a combination with HfO2 (2% strength) thermally stabilizes the powder and sets the appropriate color. Also so-called agglomerated powder in which fine powder (average particle size 10 microns and less) is compressed to agglomerates (average grain size typically 50 microns) can be used.

pure However, Al2O3 is sufficient in most cases and easiest to apply.

This Coating process involves only the heat influence in the flame of the spray head or for the preparation the glass surface to be coated. Residual moisture and / or Impurities must be eliminated beforehand. By this reduction of the applied thermal energy is a Influence or damage to the glass and surrounding Components reduced or completely avoided.

basics An innovation in coating technology in lamp construction is the use of solvent-free processes without the use manage organic compounds or liquid substances. Next the simplification of the process by the elimination of paste production environmental and occupational safety aspects are decisive.

The to be applied thermal spray process with plasma flame, Flame spraying with fuel gas flame or by high-speed flame spraying carried out. The selection of the best method depends from the glass and powder selection, as well as the thickness and the mechanical properties of the layer to be produced. By The acceleration of the powder in the flame will increase the abrasive effect of Particles avoided and the service lives of the corresponding machine parts increased.

A Significant quality improvement with simultaneous reduction the environmental and workplace hazard is through this novel application possible. Also the production costs be through the use of modified thermal spraying lowered.

The In addition, novel methods even allow not only ceramic particles such as ZrO2 or Al2O3, to be processed purely.

It is also possible to use mixtures of Al ₂ O ₃ with additional amounts of MgO and / or Y ₂ O ₃ .

• • Vorheizen des Kolbens auf Temperaturen zwischen 200 und 800°C, insbesondere 300 bis 500°C;
• • Pulver mittels Flamme aufschmelzen und auf die Oberfläche des Kolbens aufspritzen.

In principle, only two measures are required as process steps:

• • preheating the flask to temperatures between 200 and 800 ° C, especially 300 to 500 ° C;
• • Melt the powder with a flame and spray onto the surface of the piston.

This thermal spray process offers a number of specific advantages over the known processes. These are summarized in the following table. with paste according to the prior art thermally sprayed surface quality Powder only sintered, grains in size and geometry in initial state available Granules melted and fused to new, compact ceramic layer porosity very porous, poor adhesion within the layer slight porosity, cohesion of the layer very good layer thickness due to porosity and grain layer always rough, greater variations in layer thickness Layer thickness evenly, no grain size, less roughness, edge Edge is created by brushing process, not reproducible reproducible edge that can be generated with a definable transition layer thicknesses because of poor adhesion within the layer are not arbitrarily thick or thin layers can be produced; typically 100 μm Layer thicknesses typically 70 to 500 μm;

Especially If the coated pistons are bulb bulbs Quartz glass or toughened glass. The layers will be on the whole Piston applied. Usually, the piston is a discharge vessel Quartz glass.

in principle the method is also applicable to ceramic pistons.

Of the Color rendering index of high pressure discharge lamps with discharge vessel Quartz glass is about 10 points lower than comparable ones Lamps with a ceramic discharge vessel. the however, faces that discharge vessel can be made cheaper from quartz glass. The aim is therefore, even with discharge vessels of quartz glass similarly high values for the color rendering index as in the case of ceramics.

At it is known, on the ends of discharge vessels From quartz glass so-called heat dust deposits apply. Such per se known Wärmestaubeläge be now on the whole volume of the discharge vessel, as far as it serves the light emission, applied. That's it important to make the coating translucent Properties obtained by choosing the layer thickness suitable becomes.

While the production of the discharge vessel made of quartz glass Now can be a simple coating process without much extra effort be applied. In particular, the so-called. ceramic flame spraying as mentioned above. Except a high color rendering index will result in higher maintenance and achieved a lower color scattering.

characters

in the The following is the invention based on several embodiments be explained in more detail. Show it:

1 a metal halide lamp in side view;

2 a schematic representation of a method for applying the layer;

3 to 4 further schematic representations of alternative methods for applying the layer

Description of the drawings

In 1 is schematically a 1600 W high pressure discharge lamp 1 shown without outer bulb, as for example in U.S. Patent 5,142,195 is described in more detail. It is intended for use in reflectors, being arranged axially to the reflector axis.

The discharge vessel 2 of quartz glass defines a longitudinal axis X and is designed as a barrel body. The discharge volume is about 20 cm ³ . The rod-shaped tungsten electrodes 6 with deferred spiral 7 as a head are at the two ends of the discharge vessel in bruising 5 axially aligned. The electrodes 6 are on slides 8th in the bruise 5 attached to which external power supplies 9 begin. At the discharge distant end 3 the two bruises 5a . 5b is a ceramic base 11 attached with putty. The discharge vessel 2 contains a filling of a noble gas as starting gas, mercury and metal halides. The metal halide used is HgBr2 and HgJ2 as well as the light-active filling NaJ, CsJ, T1J and DyJ3 and TmJ3.

The Whole light emitting volume is covered with a layer of Al2O3 evenly covered, which is so thin about 100 to 200 microns thick that they are still translucent is. It is made by flame spraying.

• • Vorheizen des Kolbens auf Temperaturen von etwa 300 bis 400°C im Falle von plasmagespritzten Al2O3-Schichten. Die genaue Vorheiztemperatur ist abhängig von Geometrie und Masse des zu beschichtenden Entladungsgefäßes, von der Art der Keramik und von dem gewählten Spritzverfahren und der resultierenden Flammentemperatur. Bei flammgespritzten Al2O3-Schichten können Temperaturen bis zu 800°C notwendig sein.
• • Al2O3-Pulver mittels Plasmaflamme aufschmelzen und auf die Oberfläche des Kolbens lokal aufspritzen.

The coating 9 has a layer thickness of 150 microns, with a uniformity of at least 10% and is prepared as follows:

• • Preheat the flask to temperatures of about 300 to 400 ° C in the case of plasma sprayed Al2O3 layers. The exact preheat temperature depends on the geometry and mass of the discharge vessel to be coated, the type of ceramic and the chosen spraying process and the resulting flame temperature. Flame-sprayed Al2O3 layers may require temperatures of up to 800 ° C.
• • Melt the Al2O3 powder with a plasma flame and spray it onto the surface of the flask locally.

A big advantage of the new method is that it can be used selectively to coat larger surfaces, such as a layer analogous to that in US Pat. No. 4,012,655 or EP0361198 or US5003214 described, but with the difference that the porosity of the layer can be adjusted by means of flame spraying. The porosity is in a range of 10 to 50% of the layer volume. Taking other methods such as sol-gel, the porosity is close to zero. For pastes, it is very high and is about 80%. In addition, the useful layer thicknesses produced are very small, they are usually at 0.1 to 10 microns. Thicker layers, such as those which can be produced by flame spraying, whereby high throughput rates are now possible in contrast to sol-gel processes or paste processes, are in the range from 70 to 500 μm, preferably up to 200 μm. In particular, Al2O3 layers, which show more heat-retaining properties, can be applied. These are decisively supported by the porosity of the layer.

When Method is suitable for normal flame spraying, as known per se around relatively layers of typically 70-500 microns thickness applied. It is particularly inexpensive. Possible are also other flame spraying techniques such as plasma flame spraying or High-velocity flame spraying.

In flame spraying according to 2 becomes a spray nozzle 14 used, where a central channel is the powder 15 feeds and a tapered, outboard channel 21 supplying the fuel-oxygen mixture. This nozzle is directed to the surface of the piston. The metal oxide to be sprayed 15 is due to a fuel gas oxygen flame 16 melted and by the pressure of the fuel gases on the piston 17 sprayed on and forms a layer there 19 , Additionally it can support pressurized gas 18 be used. The fuel-oxygen mixture 23 is through an inner channel 21 , the compressed air through an outer channel 22 in the direction of flame 16 guided. The metal oxide 15 is supplied as a powder, which is continuously fed. By using compressed air nozzles, the flame shape and the shape of the spray jet can 20 as well as the flame temperature are controlled. The temperature reached in the flame is 2000 to 3000 ° C.

In high-speed flame spraying according to 3 the spray powder is in the spray jet 20 sprayed on the piston at a very high speed. The nozzle 24 is in particular water-cooled 25. The temperature in the flame 16 is typically 3000 ° C. It is advantageous that good adhesion and low porosity of the layer can be achieved by the high speed. In the inner channel 21 the fuel gas / oxygen mixture is supplied, in the outer channel cooling air 22 ,

In plasma spraying according to 4 becomes the energy necessary for melting the metal oxide through a plasma gas 35 generated. On a centrically arranged, water-cooled ( 36 ) Anode 37 A gas-stabilized arc of high energy density burns from copper, starting from a tungsten cathode 39 , The added gas 35 ionizes to the plasma and leaves the burner nozzle 14 at high speed and high temperature, typically 15000 ° C. The metal oxide powder is passed through channels by means of a carrier gas 34 into the plasma flame 38 introduced, melted there and then at a speed of about 300 to 700 m / s on the piston 17 thrown around there the shift 19 to build.

Such per se known spray methods have hitherto been used almost exclusively for the production of mechanically stressed protective layers, usually on metallic substrates. Only a few publications deal with specific applications for substrates made of glass or glass ceramic, for example: Kriven et al., Cer. Closely. And Sci. Proc. Vol. 24, pp. 601-614 (2003) such as Kucuk et al, J. Am. Ceram. Soc. Vol. 84, pp. 693-700 (2001) ,

The The above-described methods are for use in the lamp industry modified. The aim of the modifications is the heat input and to reduce the deformation of the lamp body or to avoid. So it is necessary to spray parameters to that effect to adapt or to modify the burner technology that the thin-walled glass vessels not by punctual Heat damage to be damaged. Goal of all thermal Injection processes is the homogeneous application of heat to distribute the surface to be coated.

Further Adjustments need to be in terms of size the surfaces or components to be coated are taken. usual Burner and spray equipment are for the small coatings usually oversized in terms of heat input and spray cone.

With a complete coating or coating of Al2O3, the following data can be obtained for an 80 W lamp with a color temperature of 3250 K, ie WDL filling with NaJ, Tl-iodide, Dy-iodide and Tm-iodide:
General color rendering index Ra = 89-90 / without coating Ra = 75
Color rendering index R9 = 14 / without coating: R9 = -70
Maintenance after 1500 hours: 100% / without coating 85%.

The Scattering of the color temperature is extremely low and is + -30 K.

The Coating is preferably made of Al 2 O 3, the layer thickness is while 100 to 200 microns.

Previous WDL fillings with discharge vessel made Quartz glass regularly reached only one Ra of about 70, the R9 was R9 = -100.

The Using ZrO2 as a coating has not proven because it is not sufficiently translucent or translucent can be.

The unique advantage of the novel coating is that it allows the temperature of the cold spot to be increased while, at the same time, keeping the temperature of the hot spot approximately constant, compared to a similar lamp having only the known thermal dust saw. The lamp has a high wall load of at least 22 W / cm ² .

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - US 5003214 A [0002]
• - US 4012655 A [0002, 0033]
• GB 1375081 A [0003]
• US 5142195 [0029]
• EP 0361198 [0033]
• US 5003214 [0033]

Cited non-patent literature

• Kriven et al., Cer. Closely. And Sci. Proc. Vol. 24, pp. 601-614 (2003) [0038]
• Kucuk et al, J. Am. Ceram. Soc. Vol. 84, pp. 693-700 (2001) [0038]

Claims (5)

High-pressure discharge lamp with a discharge vessel, which contains a filling and electrodes, wherein the discharge vessel is made of quartz glass and wherein the discharge vessel is provided with a layer of a metal oxide, characterized in that the layer of Al 2 O 3 alone or in mixtures containing predominantly Al 2 O 3, is manufactured and translucent and completely covers the light-emitting area of the discharge vessel. High-pressure discharge lamp according to claim 1, characterized characterized in that the layer thickness is 70 to 500 μm, in particular up to 200 microns. High-pressure discharge lamp according to claim 1, characterized characterized in that the layer has a porosity of 10 up to 50% of the layer volume. High-pressure discharge lamp according to claim 1, characterized in that the lamp has a filling which gives a warm white color temperature. High-pressure discharge lamp according to claim 1, characterized characterized in that the layer by means of a thermal injection molding process is made.