EP2618362B1 - Light emitter and method for its operation - Google Patents

Description

The present invention relates to the term claimed above and thus relates to bulbs.

In the present case, light sources are sources of visible, ultraviolet or infrared optical radiation which are operated with electrical energy.

In principle, it is desirable to illuminate bulbs with a reasonable energy consumption very bright. It has already been proposed to excite a gas volume by supplying electrical high-frequency energy so far that a luminous plasma is formed.

When using a high-frequency alternating field for excitation, it should be noted that the exciting field in the gas-filled space in which the plasma is ignited, not in all places has a strength that is sufficient for plasma ignition. Rather, the electromagnetic field used for plasma excitation has a spatially limited penetration depth when the high-frequency alternating field is coupled in transmission or surface wave, which is particularly strong in lamps operated with medium and low pressure plasmas with pressures up to several 100 mbar; Such lamps are of particular importance for industrial applications, as UV lamps, energy-saving lamps and fluorescent lamps. Especially with bulbs in which the discharge spaces should remain free of electrodes or - for example, the use of chemically unstable or aggressive substituents - must, so the low penetration depth of the exciting alternating electromagnetic fields is observed.

The low penetration depth causes a comparatively low heating of the gas in the discharge space. If it is not possible with a given power to ensure a sufficient temperature for a plasma discharge in the entire discharge space, either a higher power must be coupled or a drop in the efficiency can be accepted.

However, in order to operate a light source with high efficiency, various types of coupling have already been proposed.

So is a device for plasma excitation with microwaves for example from DE 103 35 523 B4 in which a microwave conductor feed line is branched and thereon are formed stick electrodes whose length leads to a microwave phase shift.

Another plasma generating device using microwaves is known, for example, from US Pat US 4,908,492 , There is proposed a cylindrical RF conductor arrangement with a cylindrical outer conductor and a helical inner conductor, between which microwave energy is supplied. Within the helical coil, a discharge tube is to be arranged. Limitations on dimensions and the form should be eliminated and sufficient energy should be able to be coupled into the gas or plasma. The use is mentioned as a high-brightness, short-wavelength light source for the purpose of optical reactions.

From the US 5,072,157 For example, a discharge tube assembly with an excitation device and a discharge tube is known, which is formed of translucent, dielectric material. The excitation device is designed to excite surface waves in the filling of the discharge tube. In this case, at least one impedance matching network is provided between a coupling-in point and a high-frequency power source.

From the US 4,049,940 An apparatus is known in which a plasma is generated in a gas column by exciting a surface wave with high frequency energy. The surface acoustic wave generating means for RF energy coupling extends only over part of the gas column and so much power is provided in the exciting electric field that the generated plasma expands beyond the corresponding part of the gas column. In one embodiment, the gas column is comprised in an elongate, insulated housing, wherein a first metallic tube, which is open on both sides, and a second tube, which surrounds the first, so that a coaxial arrangement is obtained, are provided.

From the essay " M Kando, T. Fukaya, Y. Ohishi, T. Mizojiri, Y. Morimoto, M. Shido and T. Serita, in J. Phys. D: Appl. Phys. 41 (2008) 144026 (10pp) is another excited with microwave energy lighting.

The DE 10 2009 022 755 A1 describes a high frequency lamp for low and high pressure applications that seeks to improve properties in terms of efficiency, emission spectrum, cost and longevity. For this purpose, in a high-frequency lamp, a high-frequency signal is coupled via a shielded RF line circuit in a designated as ionization glass flask, wherein one or two electrodes in a surrounded with quartz glass and filled with gases or optionally metal vapors and / or halogens ionization protrude or surrounded with quartz glass and externally contact ionization chamber filled with gases and optionally metal vapors and / or halogens and / or sulfur to effect ionization. This known lamp is supposed to be used as a high-pressure as well as a low-pressure gas discharge lamp; It wants to be distinguished by the fact that, depending on the design, it has a small point-shaped or a large spherical ionization region with large current flows and thus high color temperatures with a coverage of up to several square decimeters, so that the setting of the light output can allegedly be varied over a large range.

Mention should be further the the KR 2004 / 0107335A , This shows a flowed through by cooling water and thus particularly high heat losses subjected UV lamp.

The WO 03 / 047318A1 shows a lamp with centrally located feed antenna. No information is given about the conditions in the area of the feed-in antenna. The same applies to EM Barkhudarov et al. in "Killing Bacteria present on surfaces in films or droplets using microwave UV lamps", ISSN 1573-0972 ,

In GB 2 400 975 A is a lamp with a arranged between two coaxial cylinders discharge space is known, wherein the space provided inside clear space is open on both sides. The same applies to the lamp according to DE 39 13 519 A showing a curing system for a fiber.

Reference is also made to the JP HO6 203807 , the JP 2004 127538A , the US 2004 / 004422A1 and the US 2011 / 279065A1 , Reference is also made to the article " Compact Sulfur Lamps Operated by Antenna-Excited Microwave Discharge "by Takafumi Mizojiri, Mitsuru Ikeuchi, Yukihiro Morimoto, and Masashi Kando in the Japanese Journal of Applied Physics, Vol. 47, No. 10, 2008, pp. 8012-8016 , It describes a sulfur lamp with antenna excitation microwave discharge.

Furthermore, the inventor of the present application has proposed a luminous means and a method for operating a luminous means, in which high-frequency waves are coupled into a gas volume for generating and maintaining plasma with only little shadowing, a small construction is achieved, broadband transmissivity for high-frequency waves in the Component is guaranteed, the self-consumption or idle consumption is very low and the high-frequency wave can be easily transported into the interior of the bulb. For this purpose, in a light source with a gas volume and a coaxial RF energy coupling device be provided for exciting the same with surface waves, that the coaxial RF energy Einkopplungsvorrichtung has a guided in the gas volume central conductor.

While the various launchers may in part enable operation with reasonably high efficiency, it is desirable to further increase it and / or to obtain it with other electrode geometries and so on.

In view of the fact that the temperature in the discharge space of the luminous means influences the efficiency, it has also been proposed to provide the luminous body with a means for reducing the heat losses. It was provided around the discharge space around a vacuum to reduce wall losses. This is especially, but not exclusively, known from High Intensity Discharge lamps. The thermal insulation reduces convection losses on the lamp body.

Furthermore, it has also been proposed that lamps be actively cooled, which makes it possible to couple very high powers and, moreover, contributes to a thermal stabilization. The cooling of lamp bodies can take place here by a fluid flow and is for example common in systems for UV curing of paints.

Another type of thermal stabilization of luminaires provides to rotate the lamp body. This is known, for example, from sulfur lamps, in which the complete discharge vessel is rotated to avoid local overheating, which is technically complicated.

The object of the present invention is to provide new products for commercial use.

The solution to this problem is claimed in an independent form. Preferred embodiments can be found in the subclaims.

According to a basic idea of the invention, an arrangement according to claim 1 is thus proposed.

Based on the knowledge that when the coupling is close to the wall and at the location of coupling prevails a relatively high temperature, the coldest point of a discharge space according to the prior art no longer necessarily on the outer wall must be, an embodiment of the bulb is proposed which helps to increase the temperature of the gas discharge or to stabilize the temperature thereof.

For this purpose, it is exploited that a space at least partially enclosed by the discharge space brings less heat losses. On the one hand, the convection is reduced. This is true even if the enclosed space is only partially enclosed. Even then, heat removal from the region of high temperature in the discharge space is already substantially reduced, because particles from the region of particularly high temperature are prevented by the wall from unconfined convective and / or diffusion movement into a colder zone. It should also be mentioned that the enclosed space does not necessarily have to be a cavity. Rather, the enclosed space also with Be filled with material, such as glass or other material, where it may be completely or partially filled. It should be noted that due to the presence of a solid material, although due to the lower gas compared to a region of reduced pressure pressure even more heat energy flows out of the gas discharge zone during a start-up phase, but that after warming the central region, the heat balance just by the higher heat capacity is stabilized better. This results in particular advantages if the gas discharge is operated for a long time and an initial startup behavior is uncritical or can be compensated. It should be mentioned that possibly walls, for example, can be made particularly thick so as to be able to avoid the introduction of additional material with deviating from the vessel body expansion coefficient and the associated disadvantages and nevertheless provide an increased heat capacity.

So there is a stabilization of the temperature in the bulb interior. In this way, a particularly favorable operation can be made possible without moving parts in an electrodeless excitation. This arrangement is suitable for bulbs.

It should be noted that the space at least partially enclosed by the discharge space can be configured geometrically in such a way that a desired area results in the discharge chamber in which the gas discharge takes place. This allows a certain power density. It is typically no separate heat supply or removal required.

Since the space from the discharge space is at least partially enclosed, at the same time the heat loss is minimized by radiation, since at least a portion of the reaching into the at least partially enclosed space thermal radiation passes back into the discharge space. Even if the boundary wall between partially enclosed space and discharge space for the wavelength of the respective heat radiation is not or not completely transparent, it will heat up and accordingly emit heat radiation of different wavelength at least in part to an opposite boundary wall, so that at least by re-absorption a reduction in radiation is obtained.

It is therefore possible only by the inventive design of the lamp body and without providing additional moving parts to increase the temperature in the gas discharge interior and to stabilize, provide a desired power density in electrodeless operation and to allow a total of high efficiency.

It is advantageous if a pressure below the atmospheric pressure prevails in the space at least partially enclosed by the discharge space. In such a case, the heat dissipation from the boundary wall is further reduced by heat removal, because first to allow a negative pressure of the discharge space at least partially enclosed space against the environment must be completely completed, which even further reduces convective heat exchange. Moreover, even by reducing the pressure itself, the convective heat exchange, for example to the end faces, is reduced. It is therefore obvious that it is particularly advantageous if the at least partially enclosed by the discharge space Space is a vacuum space, preferably at a pressure of less than 1/10 of the standard atmospheric pressure. Because of the greater severity of the effects described, it is particularly preferred not to select the pressure above 1/100 of the standard atmospheric pressure; even more preferable is to use a pressure around or below 1/1000 of the atmospheric pressure. Still further reduced pressures are usable; however, the described positive effects are no longer significantly more pronounced, while at the same time increasing the technological effort. It may be mentioned that the enclosed space may optionally be filled with a certain gas under reduced pressure.

It is advantageous if the means for microwave coupling are provided for exciting a plasma light. As stated, regardless of the often low penetration depth, a high power density can be achieved by the design according to the invention. It is also provided according to the invention that the microwave coupling takes place with discharge space free of electrodes, through the outer wall of the discharge space. This allows the choice of the medium present in the discharge space to be made irrespective of whether chemical reactions occur with materials typically used for electrodes. Thanks to the simultaneously possible by the geometric design adjustment of the power density, the invention thus opens up considerable freedom in terms of the choice of the existing medium in the discharge space, which offers quite significant advantages for the achievement of a particular spectrum to be radiated. It is possible that the luminous element is formed from glass, quartz glass and / or glass ceramic. This is advantageous because it allows the use per se of long known and proven materials and, accordingly, the use as per se reliably known manufacturing method.

It is advantageous if the discharge space is arranged at least partially coaxially with the space at least partially enclosed by the discharge space. In other words, the enclosed space will be central and the discharge space will be arranged around it. That a central arrangement is also possible where the outer wall of the discharge space is not cylindrical, but, for example, flattened or the like, should be mentioned.

It may also be mentioned as advantageous that the space at least partially enclosed by the discharge space is completely enclosed by the latter at least on one side, preferably on both sides. Thus, the advantages of the invention result in particular.

Fig.1 a-c

verschiedene erfindungsgemäße Anordnungen von Entladungsraum und davon zumindest partiell umschlossenem Raum;

Fig. 2

eine perspektivische Darstellung zur Ausführungsform von Fig. 1a.

The invention will now be described by way of example only with reference to the drawings. In this is represented by:

Fig.1 ac

various inventive arrangements of discharge space and at least partially enclosed space;

Fig. 2

a perspective view of the embodiment of Fig. 1a ,

To Fig. 1 a luminous means comprises a luminous body which a discharge space 1 and a means for thermal stabilization 2, which is formed as a space 2 at least partially enclosed by the discharge space 1.

The light-emitting means 1 has external electrodes (not shown), which are arranged on the outer wall of the discharge space 1 in per se known manner and feed high-frequency energy into the substances present in the interior of the discharge space. The outer electrodes (not shown) are connected to a suitable high frequency power source of sufficient power.

In one embodiment, the discharge generating bulb has been filled with, for example, indium-argon to achieve discharge with indium iodide as a carrier to achieve the required partial pressures of the indium.

The luminous element is made of quartz glass in the present embodiment.

In Fig. 1a Here, an embodiment is shown in which a cylindrical quartz glass body is formed with vertical to the cylinder wall end faces, which are also made of quartz glass. In the interior of this quartz glass body with a cylindrical outer wall, an inner cylinder coaxial with the outer quartz glass body is now provided, which is also closed at its end faces by the vertical end faces of quartz glass (in FIG Fig. 2 not shown) .

Thus, by the cylinder wall of the coaxial inner cylinder and the vertical end surfaces of quartz glass is a closed, formed central space and formed by the cylinder wall, a boundary wall between the discharge space 1 and at least partially enclosed by this space 2.

It should be mentioned that here - as in particular in the other embodiments also - the geometric design can be chosen so that there is a certain gas discharge cross-section and thus optimal power density can be used.

The partially enclosed by the discharge space and against the ambient atmosphere through this together with the vertical end surfaces of quartz glass completely sealed against the ambient atmosphere space is evacuated, here - as preferred - to a pressure of less than 1/10 of the standard atmospheric pressure.

During operation, power is coupled into the discharge space via the outer electrodes, where a plasma discharge occurs close to the outer wall and accordingly the highest temperatures occur near the outer wall.

The plasma discharge generated by the high frequency power has its hottest point away from the central axis of the cylinder. Due to the temperature gradient less heat radiation is received from other areas in the direction of the central axis as in this emitted. A considerable part of the radiation emitted in the space 2 partially enclosed by the discharge space 1 will, however, pass through this partially enclosed space 2 in such a way that it again enters the discharge space 1 on the opposite side, where the radiation Moreover, some can be absorbed again, for example, from the plasma present there. Since the pressure in the space 2 partially enclosed by the discharge space 1 is small, the otherwise occurring convective heat transport to the end surfaces made of quartz glass is also correspondingly irrelevant. The total heat loss of the arrangement according to the invention is thus low. The space partially enclosed by the discharge space 1 thus serves for thermal stabilization and can thus be regarded as a means for thermal stabilization.

In the embodiment of Fig. 1b is one of the two cylinder end faces of the discharge space, which in Fig. 1a closed by flat round quartz glass plates, completed by a hemispherical rounding. In addition, the boundary wall between the discharge space 1 and the partially enclosed by this space 2 is also continued by a hemispherical rounding end. The distance between the outer wall and boundary wall is chosen to be as large here in the area of the hemispherical rounding as on the cylinder jacket area.

In Fig. 1c is also the second of the two cylinder end faces in Fig. 1a closed by flat round quartz glass plates, replaced by a hemispherical conclusion of the discharge space. Again, the boundary wall between the discharge space 1 and the partially enclosed by this space 2 is also formed by a hemispherical curve. Again, the distance between the outer and boundary wall in the region of the hemispherical curves here chosen to be as large as the cylinder jacket area. It encloses so in the embodiment of Fig. 1c the discharge space 1 the thermally stabilizing space 2 here completely.

This results in comparable effects as in the embodiment of Fig. 1a , Once again, the space 2 enclosed by the discharge space 1 has a thermally stabilizing effect during operation; the stabilizing effect is - but even better - according to the more complete enclosing.

In summary, a new illuminant has thus been proposed above, in which a separate space for thermal stabilization is provided in the interior of the discharge space. As a result, variations in the ambient temperature in turn have less effect and inhomogeneities in the discharge can at least be reduced. This also applies if - as with bulbs with electrode-free discharge spaces - the assumption is no longer true that the temperature profile drops starting from the center of a discharge.

By dimensioning and shaping of the discharge vessel and the vacuum space, the power density of the excitation power of the gas discharge resulting from a luminous means can easily be optimized. Since at the same time by the present invention, substances are used for the first time or at least easier, their partial pressure is set in the discharge by the existing temperature and would be too cold spots, the design of bulbs undergoes significant relief and enhancements. In particular, it becomes possible to provide mercury-free lamps, which offers particular advantages.

It should be noted that, although the above description has mainly referred to a lamp, the thermal stabilization of a gas discharge vessel by a space separated from the discharge space can also bring advantages where it does not depend on the emission of visible radiation, but a gas discharge other reasons is needed.

Claims (8)

1. Lighting means
   comprising a lighting body having

   an electrodeless discharge chamber (1) which comprises an outer wall and into which microwaves are coupled,

   and

   thermal stabilisation means comprising a chamber (2) that is

   separated from the discharge chamber (1) by a partition,

   at least partially surrounded by the discharge chamber (1)

   and central with respect to the discharge chamber (1),

   characterised in that

   outer electrodes are provided at the outer wall of the discharge chamber (1) configured to couple microwaves into the discharge chamber (1) through its outer wall

   and

   the chamber (2), which is at least partially surrounded by the discharge chamber (1), is a closed vacuum chamber or is filled with solid material so as to reduce heat dissipation from the discharge chamber through the partition defining the discharge chamber.
2. The lighting means according to claim 1, characterised in that the chamber (2), which is at least partially surrounded by the discharge chamber (1), is a closed vacuum chamber having a pressure of less than 1/10 of standard atmospheric pressure, preferably of less than 1/100 of standard atmospheric pressure.
3. The lighting means according to claim 1, characterised in that the chamber (2), which is surrounded at least partially by the discharge chamber (1), is filled with glass.
4. The lighting means according to any of the preceding claims, characterised in that the outer electrodes are configured to couple in microwaves for exciting plasma luminescence.
5. The lighting means according to any of the preceding claims, characterised in that the lighting body is formed of glass, fused quartz glass and/or glass ceramics.
6. The lighting means according to any of the preceding claims, characterised in that the discharge chamber (1) and the chamber (2), which is at least partially surrounded by the discharge chamber (1), are arranged coaxially with respect to each other.
7. The lighting means according to any of the preceding claims, characterised in that the chamber (2), which is at least partially surrounded by the discharge chamber (1), is completely closed by the latter at least on one side.
8. The lighting means according to any of the preceding claims, characterised in that the chamber (2), which is at least partially surrounded by the discharge chamber (1), is completely enclosed inside the discharge chamber.

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