WO2007077504A2 - Lampe à décharge de vapeurs de mercure à haute pression et procédé de fabrication d’une lampe à décharge de vapeurs de mercure à haute pression - Google Patents

Lampe à décharge de vapeurs de mercure à haute pression et procédé de fabrication d’une lampe à décharge de vapeurs de mercure à haute pression Download PDF

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Publication number
WO2007077504A2
WO2007077504A2 PCT/IB2006/054974 IB2006054974W WO2007077504A2 WO 2007077504 A2 WO2007077504 A2 WO 2007077504A2 IB 2006054974 W IB2006054974 W IB 2006054974W WO 2007077504 A2 WO2007077504 A2 WO 2007077504A2
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WIPO (PCT)
Prior art keywords
pressure mercury
electrode
mercury vapor
electrodes
discharge vessel
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PCT/IB2006/054974
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English (en)
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WO2007077504A3 (fr
Inventor
Pavel Pekarski
Holger Moench
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Philips Intellectual Property & Standards Gmbh
Koninklijke Philips Electronics N.V.
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Publication of WO2007077504A2 publication Critical patent/WO2007077504A2/fr
Publication of WO2007077504A3 publication Critical patent/WO2007077504A3/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00—Gas-discharge or vapour-discharge lamps
    • H01J61/84—Lamps with discharge constricted by high pressure
    • H01J61/86—Lamps with discharge constricted by high pressure with discharge additionally constricted by close spacing of electrodes, e.g. for optical projection
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00—Gas-discharge or vapour-discharge lamps
    • H01J61/02—Details
    • H01J61/04—Electrodes; Screens; Shields
    • H01J61/06—Main electrodes
    • H01J61/073—Main electrodes for high-pressure discharge lamps
    • H01J61/0732—Main electrodes for high-pressure discharge lamps characterised by the construction of the electrode
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/24—Manufacture or joining of vessels, leading-in conductors or bases
    • H01J9/245—Manufacture or joining of vessels, leading-in conductors or bases specially adapted for gas discharge tubes or lamps
    • H01J9/247—Manufacture or joining of vessels, leading-in conductors or bases specially adapted for gas discharge tubes or lamps specially adapted for gas-discharge lamps

Definitions

  • the invention relates to a high-pressure mercury vapor discharge lamp comprising an envelope of a material capable of withstanding high temperatures with a discharge vessel and two electrodes extending from two sealing sections into the discharge vessel and having an electrode gap smaller than or equal to 2.5 mm, preferably smaller than or equal to 1.5 mm.
  • the discharge vessel contains a filling which essentially comprises rare gas, oxygen, halogen, and mercury.
  • the halogen is chlorine, bromine, iodine, or a mixture thereof.
  • Mercury is present in a quantity of more than 0.15 mg/mm 3 .
  • the invention relates to a method of manufacturing such a high-pressure mercury vapor discharge lamp.
  • An arc is ignited for generating light between the two electrodes of the high- pressure mercury vapor discharge lamps.
  • Such lamps are referred to as short-arc lamps because of their small electrode gap.
  • the mercury evaporates in operation and with a quantity of 0.15 mg/mm 3 usually provides a mercury vapor pressure of approximately 150 bar in the lamp.
  • An example of a high-pressure mercury vapor discharge lamp of such a type -but with a still higher mercury portion - is described in DE 381 34 21 Al.
  • Such lamps having mercury vapor pressures above 100 bar produce a high luminance and a relatively continuous spectrum.
  • these high-pressure mercury vapor discharge lamps are often denoted UHP lamps, wherein UHP means "Ultra High Pressure” because of the high pressure or "Ultra High Performance” because of the high luminance.
  • UHP means "Ultra High Pressure” because of the high pressure or "Ultra High Performance” because of the high luminance.
  • a major field of application of these lamps is the use in projection systems.
  • the high electrode load of the lamps has the effect that the tungsten evaporates from the electrodes and is deposited on the wall of the discharge vessel. This leads to a blackening of the envelope, as a result of which the latter is strongly heated, which may give rise to an explosion of the envelope, particularly at high mercury vapor pressures. With the aforementioned lamps, this is yet compounded by the relatively small dimensions of the envelope or the discharge vessel. Therefore, such a blackening of the wall should be avoided at all cost.
  • the high-pressure mercury discharge lamp comprises, as mentioned, a small quantity of at least one of the halogens chlorine, bromine, or iodine. These halogens create a tungsten transport cycle by which the tungsten deposited on the wall of the discharge vessel is transported back to the electrodes.
  • electrodes which comprise a thin tungsten rod having a thick, solid electrode head or a coil at its front end, which coil is wound around the tungsten rod.
  • the tungsten rod itself may be helically wound at the end.
  • DE 381 3421 Al cited above shows examples of this.
  • Such a relatively thick electrode head serves to ensure that electrode stability is guaranteed over a wide current range, i.e. during starting-up and during operation of the lamp, and that radiation cooling is improved.
  • a typical diameter of such an electrode head in classical UHP lamps is between 800 ⁇ m for IOOW UHP lamps and 2000 ⁇ m for 275 W UHP lamps.
  • the electrode end at the other side i.e. the end of the electrode connected to a molybdenum foil and sealed within the respective sealing section, should be as thin as possible for two reasons.
  • a thinner electrode end reduces the heat transfer into the sealing section and thus prevents a quartz re-crystallization when the usual quartz glass is used for the lamp envelope.
  • Typical solid electrodes with thick heads have conical tips, whereas the rod winding electrodes usually have tips extending forward at the front of the coil (for example, see the cited DE 381 3421 Al).
  • Such a tip is essential in stabilizing the arc discharge for two reasons: During operation of the discharge lamp, temperatures above the melting point of tungsten should be obtained in the region of the electrode tip in order to obtain a sufficient thermionic emission from the electrode surface. It is clear that in case of electrodes having definitely shaped thin tips, this tip region can be brought to the necessary melting point temperature with a smaller input power than in the case of flat electrode surfaces.
  • the electrode tip defines a stable position for establishing the arc discharge, whereas a flat electrode surface provides a plurality of possible contact points for an arc discharge, so that jumping of the arc discharge (fluttering) will constitute a substantial problem.
  • manufacture of such electrodes having solid heads or a defined coilwith an accurately designed tip involves a significant cost, which increases the total price of the high-pressure mercury vapor discharge lamps.
  • the object is achieved by a high-pressure mercury vapor discharge lamp according to claim 1 and by a method according to claim 8.
  • a high-pressure mercury vapor discharge lamp has an envelope of high-temperature-resistant material, preferably quartz glass, or possibly aluminum oxide.
  • This envelope has a discharge vessel and two electrodes, preferably made of tungsten, extending from two sealing sections at opposite sides into the discharge vessel.
  • the electrode gap is smaller than 2.5 mm, preferably smaller than 1.5 mm.
  • the discharge vessel contains, as described above, a filling which comprises the substances rare gas, oxygen, and a halogen, the latter being chlorine, bromine, iodine, or a mixture thereof, as well as mercury in a quantity of more than 0.15 mg/mm 3 .
  • the electrodes according to the invention are rod-shaped here and designed such that at the latest after a definite period of operation they each have at their tip a nipple extending in the longitudinal direction of the electrode.
  • Such simple, rod-shaped electrodes can be manufactured in a relatively economical way.
  • a suitable design i.e. the selection of suitable dimensions of such a rod-shaped or cylindrical electrode is readily capable of achieving that it has the desired nipple at the latest after said definite period of operation.
  • the length of such a nipple may reach the order of magnitude of approximately the diameter of the relevant electrode, while the dimensions of the rod-shaped electrode are selected such that the nipple is formed for its length, shape and position at the electrode tip to be essentially stable - that is, viewed on a long-term scale, apart from the usual brief fluctuations .
  • an envelope is made from a tube of high temperature resistant material, preferably quartz glass, which envelope has a discharge vessel and two residual tube sections at opposite sides of the discharge vessel. Electrodes are then inserted into the two tube sections, which electrodes are connected via respective metal strip sections, of molybdenum as a rule, to a supply line. The electrodes are positioned such that they extend into the discharge vessel and a precisely defined electrode gap of ⁇ 2.5 mm; preferably ⁇ 1.5 mm, is maintained. Then the discharge vessel is filled with the filling described above and sealed by pressing or fusing the tube sections into sealing sections, in which the metal strip sections are tightly embedded.
  • the processes of forming of the tube into a discharge vessel, of inserting the electrodes into the discharge vessel, and of filling and sealing the discharge vessel may be carried out in the usual manner.
  • a wide variety of methods is known to those skilled in the art for this purpose.
  • first one electrode may be inserted and then pressed or fused into a sealing section at this side of the tube section.
  • the halides and mercury are introduced, the second electrode is inserted at the appropriate distance to the first electrode, and the second tube section is finally sealed after filling with the rare gases.
  • the sequence of when which electrode is inserted, when the filling is carried out, and when the discharge vessel is sealed at which side is not significant for the present invention.
  • the dependent claims comprise particularly advantageous embodiments and further embodiments of the invention.
  • the method of manufacturing the high- pressure mercury vapor discharge lamp may also be designed by analogy to the dependent claims on the high-pressure mercury vapor discharge lamp, and conversely the high-pressure mercury vapor discharge lamp may also be embodied further in accordance with the dependent claims on the manufacturing process.
  • simple rod-shaped electrodes may be used, whose diameter and whose free electrode length- which is defined by the distance from the exit point of the respective electrode from the sealing section, i.e. the point of contact of the electrode with, for example, quartz glass, to the tip of the relevant electrode- are selected such that the nipples are formed automatically during lamp operation at the latest within the specific period of operation.
  • simple rod-shaped electrodes have a strong growth of such nipples at the electrode tips, and the nipples stay sufficiently stable during the entire life span of the lamp.
  • this growing nipple guarantees arc stability and reduces the power input into the electrode per current unit and thus the heat flow in the direction of the sealing sections compared with the original rod-shaped geometry.
  • rod-shaped electrodes are used here whose electrode diameters are
  • the electrode diameters are > 200, particularly preferably > 300 ⁇ m.
  • a suitable selection of such electrode diameters at the tip of the rod-shaped electrode directly behind the nipple causes tungsten accumulated there to form a swelling during operation. This results in an increase in the rod diameter at the tip directly behind the nipple and in addition a wrinkling of the electrode surface, thus providing an intensified radiation cooling of the electrode.
  • the electrode is designed such that the growth of the nipple at the electrode tip takes place in the first 30 hours of operation of the lamp, the strongest part of the growing process already taking place in the first 10 hours of operation.
  • the growing process is accompanied by a decrease in the operating voltage by more than 5 V in the high-pressure mercury vapor discharge lamp within the first 30 hours of operation.
  • the nipples by radiation with a laser at the tips of the rod-shaped electrodes already during manufacture, for example before inserting the rod-shaped electrode.
  • the diameter of the rod-shaped electrodes and the free electrode length of the relevant electrode (including the nipple) should then be selected such that during operation of the high-pressure mercury vapor discharge lamp the corresponding nipples remain sufficiently stable.
  • the dimensions should be selected exactly as described above.
  • the laser treatment merely ensures that the electrodes have nipples with the desired shape form from the outset.
  • Such a laser treatment is an additional process step during lamp manufacture, but the cost of this step is not comparable to the expense of manufacturing the electrodes mentioned above with thickened heads or helical electrodes. Thus a significantly more economical manufacture of the lamps is also possible with such electrodes.
  • the invention is applicable with high-pressure mercury vapor discharge lamps, which have an operating nominal wattage between 20 and 60 Watts, preferably a nominal wattage of approximately 40 or approximately 50 Watts.
  • high-pressure mercury vapor discharge lamps which have an operating nominal wattage between 20 and 60 Watts, preferably a nominal wattage of approximately 40 or approximately 50 Watts.
  • it relates to relatively small lamps, which could also be denoted as miniaturized high-pressure mercury vapor discharge lamps.
  • preferably adjusted parameters are the wall load of the lamp, which preferably should be > 0.7 W/mm 2 , particularly preferably >1 W/mm 2 .
  • the halogen quantity, for which bromine is preferably used advantageously lies between 10 - " 5 ⁇ mole/mm -,3 and 2 x 10 "4 ⁇ mole/mm 3 .
  • rod-shaped electrodes are preferably used whose diameter is between 220 ⁇ m and 420 ⁇ m and whose free electrode length is selected between a minimum free electrode length and a maximum free electrode length.
  • the minimum free electrode length may be calculated as:
  • both the minimum electrode length and the maximum electrode length are determined in dependence on the diameter d of the electrodes and an average operating current I of the high-pressure mercury vapor discharge lamp.
  • the current I is expressed in the unit A and the electrode diameter d, the minimum free electrode length Lm 1n , and the maximum free electrode length L max in the unit mm.
  • the average operating current I is the RMS value (Root Mean Square Value) and not the maximum current, which may be substantially higher in the case of pulsed operation.
  • the high-pressure mercury vapor discharge lamp is preferably structured such that the sealing sections of the lamp envelope have a cross-sectional area of between 6 mm 2 and 20 mm 2 , particularly preferably of approximately 10 mm 2 .
  • This has significant advantages for the thermal balance and thus the entire design of the lamp.
  • the heat conduction mechanisms and the temperature conditions in the lamp are described briefly below:
  • the length of the sealing section of the UHP lamps is determined by the temperature at the location where the metal parts of the lamp, i.e. the supply lines to the electrodes, come into contact with the ambient air. In order to avoid a fast oxidation of these parts, which usually comprise molybdenum, this location should be such that it does not become hotter than 350 0 C to 400 0 C. It is clear that the temperature decreases along the longitudinal direction of the sealing sections away from the main heat source, which is the hot discharge vessel in the center of the lamp envelope. The main mechanism heating the ends of the sealing sections is the heat conduction through the material of the sealing sections in outward directions from the center of the lamp. In addition, the molybdenum foil contributes to the thermal conduction by approximately 10 to 20%.
  • TIR total internal reflection
  • the sealing sections are cooled through the radiation of the hot material, for example in the case of a quartz glass envelope of the hot quartz material, as well as by heat conduction to the ambient air.
  • both mechanisms provide the best cooling when as large a temperature difference to air as possible is present.
  • the sealing sections are subject to additional heat, which is reflected back by radiation within a reflector or by the optical system.
  • the heating mechanism acting on the optical path within the sealing sections mentioned above as the second mechanism accounts for a very significant portion of the heating of the ends of the sealing sections.
  • the advantageous arrangement of the envelope such that the cross-sectional area lies below 20 mm 2 can considerably reduce this portion of the heat conduction - in contrast to known UHP lamps, which have at least a 25-mm 2 cross-section, or as a rule well above it. This renders it possible to design the sealing sections to be significantly smaller. Nevertheless, the temperatures in the end region of the sealing sections, where the metal comes into contact with air, remain below the desired 350 to 400 0 C.
  • the wall thickness of the discharge vessel at the thickest location of the discharge vessel, the so-termed equator of the lamp is greater than or equal to 1.3 mm, preferably greater than or equal to 1.6 mm, and particularly preferably greater than or equal to 1.7 mm.
  • the outer diameter of the discharge vessel at the thickest location is approximately 7.1 mm and the inner diameter there is approximately 3.5 mm.
  • the lamp envelope is preferably formed from a tube with an outer diameter of only approximately 4.1 mm and an inner diameter of approximately 2 mm.
  • the tube sections may be formed into the sealing sections at the discharge vessel by means of pressing or fusing, as described above.
  • fusing is the preferred method, as a greater compression strength can be achieved thereby.
  • Sealing sections are thus produced which have an essentially round diameter.
  • it is then ensured that the diameter of the sealing sections lies between 2.5 mm and 5 mm- preferably at approximately 3.6 mm- in order to obtain the desired cross- sectional area.
  • the length of the metal strip sections, which should be fully embedded in the sealing sections, is preferably ⁇ 12 mm.
  • the tube for forming the discharge vessel in the thickest location of the discharge vessel is compressed in axial direction by more than 250%, preferably by more than 300%, under simultaneous radial expansion.
  • a method of implementing such a compression is described below.
  • the high-pressure mercury vapor discharge lamps according to the invention as described above may be used in any projector system.
  • the lamps may be used particularly advantageously in a projector system for high-pressure mercury vapor discharge lamps with an elliptical reflector, which has a distance of ⁇ 50 mm, preferably ⁇ 45 mm, between its two focal points.
  • the reflectors used in projector systems until now have a substantially larger focal distance, which overall leads to a larger need for space for the optical systems in the projector housing.
  • the lamp may also be used in other applications in principle, for example in the automotive sector, in medical devices, or in other lighting sectors.
  • Fig. 1 shows a longitudinal section through a high-pressure mercury vapor discharge lamp according to a first embodiment, before the first start-up
  • Fig. 2 shows a longitudinal section through the high-pressure mercury vapor discharge lamp of Fig. 1, but after the start-up, with an enlarged schematic representation of the electrode tips
  • Fig. 3 shows a radiograph of an embodiment of a high-pressure mercury vapor discharge lamp according to the invention, after a few minutes of operation
  • Fig. 4 shows a radiograph of an embodiment of a high-pressure mercury vapor discharge lamp according to the invention after a period of operation of approximately 200 hours
  • Fig. 5 shows the dependence of the temperature T of the electrode on the distance from the electrode tip for different free electrode lengths and different electrode diameters
  • Fig. 6 is a graph showing the advantageous regions for selecting the free electrode length L in dependence on an average operating current I of the lamp for different electrode diameters
  • Fig. 7 is a graph showing the voltage drop across a high-pressure mercury vapor discharge lamp according to the invention as a function of the period of operation
  • Fig. 8 schematically shows an elliptical reflector with a high-pressure mercury vapor discharge lamp according to Fig. 1 installed therein, and
  • Fig. 9 shows a functional arrangement of the reflector with the high- pressure mercury vapor discharge lamp according to Fig. 7 in a schematically represented projector system.
  • the high-pressure mercury vapor discharge lamp 1 schematically shown in Figs. 1 and 2 and the high-pressure mercury vapor discharge lamp shown in Figs. 3 and 4 are preferred embodiments which are each operated with a rated power of approximately 50 W.
  • the lamps 1 comprise an envelope 2 of quartz glass with a centrally arranged discharge vessel 3 and two sealing sections 4 arranged at opposite sides of the discharge vessel. Electrodes 5, 6 extend into the discharge vessel 3 from the sealing sections 4. These electrodes 5, 6 are connected inside the sealing sections 4 to respective molybdenum foil sections 8, which in their turn are connected at the other ends to the supply lines 9, usually molybdenum wires.
  • the electrode gap d e i.e.
  • the discharge vessel 3 is filled not only with a rare gas, but in the present case also with argon having a pressure of 200 mbar, with oxygen, mercury, and a halide, here bromine.
  • the oxygen is present in only a very small quantity. Generally, the oxygen quantity introduced into the lamp by the surface oxidation of the metal parts will be sufficient.
  • the bromine quantity is approximately 1 x 10 "4 ⁇ mole/mm 3 .
  • the mercury is present in a quantity of more than or equal to 0.15 mg/mm 3 and less than or equal to 0.35 mg/mm 3 . In this particular preferred embodiment, the total mercury quantity is 6 mg (this corresponds to approximately 0.17 mg/mm 3 ).
  • the wall load is more than 0.7 W/mm 2 in this lamp.
  • the lamp envelope is manufactured from a quartz glass tube having an outer diameter of 4.1 mm and an inner diameter of 2 mm.
  • the shaping of the discharge vessel 3 takes place in a glass lathe, in which the tube is held at both ends in a headstock and a tailstock.
  • the tube is heated in its central region, whereupon the headstock and the tailstock are brought together in order to compress the material in the central region, at the thickest location of the discharge vessel.
  • the tube is radially widened in the heated areas by a positive pressure from the inside, for example by injecting an inert gas, so as to achieve the desired shape of the discharge vessel.
  • the exact shape of the discharge vessel may be determined from the outside through pressure by a negative mold.
  • the compression and expansion processes preferably have at least two stages, i.e. compression takes place, then stretching, then compression again, and finally stretching again. This process may be carried out for a long time until the desired shape has been obtained.
  • the finished discharge vessel then has, at its thickest location, an envelope outer diameter d a of 7.1 mm and an envelope inner diameter U 1 of 3.5 mm.
  • the wall thickness d w is thus approximately 1.7 mm. This corresponds to a compression of approximately 300% with respect to the original wall thickness of the glass tube.
  • the electrode 5, fastened at one side to the molybdenum foil and to the lead wire 9, is supplied.
  • the discharge vessel 3 is filled with mercury in the form of a mercury droplet. This usually happens in an inert gas atmosphere.
  • the second electrode 6 is then inserted.
  • the glass tube section is sealed at one side in order to produce the sealing section that is to seal off the discharge vessel 3 at this side.
  • the discharge vessel 3 is filled from the yet open side with the desired halogen, for example in the form of methyl bromide as described in DE 38 13 421 Al, and is filled with the desired rare gas, and finally the second seal is provided, whereby the discharge vessel 3 is completely sealed.
  • the electrodes are preferably positioned with the help of a monitoring system in order to maintain the exactly specified electrode gap d e .
  • the small thickness of the initial glass tube ensures on the one hand that the diameter of the sealing section 4 or the seals is only 3.6 mm, i.e. the cross-sectional area of the seal is approximately 10 mm 2 .
  • the strong compression process in forming the discharge vessel ensures that the wall thickness in the region of the discharge vessel is sufficient for withstanding high mercury vapor pressures of 200 bar and more.
  • the length of the molybdenum foils in the present case is just below 12 mm, the length of the sealing sections is only approximately 15 mm.
  • a length of the discharge vessel of approximately 7 mm it is possible to design a lamp envelope 2 having a total length of only approximately 36 to 38 mm.
  • the selected lamp dimensions, particularly the small diameter d s of the sealing sections 4 and the associated smaller cross-sectional area, achieve that the temperatures at the outer ends of the sealing sections 4 are below the permissible level of 400 0 C also with the sealing sections 4 shorter than in the known lamps. A dramatic temperature reduction at the outer ends of the sealing sections can indeed be achieved with this structure in experiments.
  • UHP lamps were constructed in the usual manner from glass tubes with a diameter of approximately 6 mm and were compared with the UHP lamps manufactured from 4-mm glass tubes as shown in Fig. 1.
  • the sealing sections of the lamps from the 4 mm tubes have half the cross-sectional area of the lamps manufactured from the 6-mm tubes. This reduction in the cross-section led to a temperature that is 100 K lower at the ends of the sealing sections.
  • the electrode diameter d and the free electrode length L from the tip of the electrode 5, 6 to the quartz glass exit point of the sealing section 4 were selected in dependence on the average operating current I such that in the course of the operation, preferably in the first 10 hours of operation, a substantially stable nipple 7 is formed at the electrode tip.
  • Fig. 2 which additionally shows an enlarged schematic cutout of the lamp 1 in the region of the electrode tips.
  • the nipples 7 achieve that the electrodes 5, 6 have at their outermost tips, i.e. in the region of the nipples 7, a sufficiently high temperature above the melting point of mercury for ensuring a sufficient electron emission.
  • Figs. 3 and 4 show radiographs of a further prototype of the lamp according to the invention.
  • Fig. 3 shows the lamp after an operation of some minutes
  • Fig. 4 shows the same lamp after an operation of approximately 200 hours.
  • the electrode gap is approximately 0.9 mm.
  • the lamp was operated at a nominal wattage of 50 W.
  • Such a lamp, according to the invention may be operated with customary drivers in pulsed operation.
  • the electrodes are at first simple rod-shaped electrodes. This may be recognized particularly well at the left electrode 5.
  • the almost spherical dot 11 is due to mercury which condenses in the cooled-off state of the lamp, usually precipitates in a drop form at the electrodes 5, 6, and evaporates again immediately after the start-up of the lamp.
  • the right electrode 6 is equally rod-shaped as the left electrode 5, but the rod shape cannot be recognized so well here owing to different mercury deposits 12.
  • Fig. 4 clearly shows how the desired nipples 7 are formed at the tips of the electrodes 5, 6 during operation.
  • tungsten deposits directly behind the tip 7 cause a swelling 10 of the electrodes 5, 6.
  • the diameter in this location increases by approximately 10%.
  • the electrode surface in this region becomes wrinkled.
  • the radiation cooling of the electrode 5, 6 is substantially improved by this swelling and wrinkling of the surface.
  • the remaining apparent swellings 13, 14 at the electrodes 5, 6 are again formed by condensed mercury, which deposits at the electrodes 5, 6 in the cold state of the lamp and evaporates again during operation.
  • the diameter d and the free electrode length L are suitably selected in dependence on the desired average operating current I. If the electrodes 5, 6 are too long, they will become very hot in the transition region during operation and as a rule break down already during the start-up of the lamp. Very short electrodes 5, 6 lead to a strong jumping of the discharge arc and in addition to a re-crystallization in the sealing section owing to a too strong heat transfer into the sealing sections 4.
  • Fig. 5 results of a simulation implemented for finding the suitable dimensions are shown in Fig. 5.
  • the electrode temperature T in K along the electrode is plotted against the distance from the electrode tip in ⁇ m.
  • the melting temperature T m of the electrode material of 3680 K is also shown.
  • the line drawn topmost shows the temperature gradient for an electrode having a diameter d of 300 ⁇ m with a free electrode length L of 3,000 ⁇ m.
  • the dashed curve below it shows the temperature gradient for the same electrode, but with a free electrode length L of only 2,500 ⁇ m.
  • the third, dotted curve shows the temperature gradient for an electrode having a diameter d of 400 ⁇ m with a free electrode length L of 3,000 ⁇ m
  • the lowest, dot and dash curve shows the temperature gradient for a corresponding electrode having a diameter of 400 ⁇ m and a free electrode length of 2,500 ⁇ m.
  • the power input to the electrode here is approximately 8 W/A.
  • the free electrode length L should be chosen within definite fixed limits in dependence on the operating current and on the electrode diameter D.
  • the upper limit value, i.e. the maximum free electrode length L max , and the lower limit value, i.e. the minimum free electrode length Lm 1n can be calculated from equations (1) and (2) given above in dependence on the diameter D of the electrode and the desired average operating current I.
  • Fig. 6 once again shows the upper and lower limit values L max , L m1n thus calculated for the free electrode length L in dependence on the current I for different electrode diameters.
  • the free electrode length L is plotted in mm against the current I in A.
  • the drawn curves show the upper and lower limits for the free electrode length L with an electrode diameter d of 300 ⁇ m
  • the dashed curves show the limit values for an electrode diameter d of 350 ⁇ m
  • the dotted curves show the values for an electrode diameter d of 400 ⁇ m.
  • This Fig. also shows that a definite electrode diameter d should be preferably selected for definite operating currents I, so that a particularly good growing process is ensured.
  • an electrode diameter d of 300 ⁇ m may be selected in a current range of approximately 0.6 A to approximately 1 A, an electrode diameter d of 350 ⁇ m preferably in a current range of approximately 0.8 A to approximately 1.2 A, and an electrode diameter d of 400 ⁇ m in a range of approximately IA to approximately 1.4 A.
  • a first high-pressure mercury vapor discharge lamp having a spherical discharge vessel is operated at 50 W and has an electrode gap of 1.3 mm.
  • the operating current is 62.5 V and the average operating current is 0.8 A.
  • Rod electrodes having a diameter of preferably 0.3 mm and a free electrode length of 2.5 mm should then be selected.
  • a second high-pressure mercury vapor discharge lamp having a spherical discharge vessel is operated at 50 W and has an electrode gap of 1 mm.
  • the operating current is 50 V and the average operating current is 1 A.
  • Rod electrodes having a diameter of preferably 0.35 mm and a free electrode length of 2.8 mm should then be selected.
  • a third high-pressure mercury vapor discharge lamp having an elliptical discharge vessel is operated at 40 W and has an electrode gap of 1.5 mm.
  • the operating current is 67 V and the average operating current is 0.6 A.
  • Rod electrodes having a diameter of preferably 0.3 mm and a free electrode length of 3.1 mm should then be selected.
  • a fourth high-pressure mercury vapor discharge lamp having an elliptical discharge vessel is operated at 40 W and has an electrode gap of 1.35 mm.
  • the operating current is 60 V and the average operating current is 0.66 A.
  • Rod electrodes having a diameter of preferably 0.28 mm and a free electrode length of 2.9 mm should then be selected.
  • the exact growing process of the nipples at the electrode tips may best be followed via a measurement of the operating voltage in dependence on the operating time. Given the same pressure and the same power, the voltage is determined by the electrode gap, and the growth of the desired nipples at the electrode tips leads to a reduction of the electrode gap, with the result that a voltage drop also indicates the growing process. This is shown in Fig. 7. Here, the operation voltage in volts is plotted against the period of operation in hours. The lamp was operated here -in order to simulate as realistic an operation as possible- for two hours each time and then cooled down again for 15 minutes. The electrode gap at the beginning of the experiment was 1.25 mm, i.e. as yet without nipples at the rod-shaped electrodes.
  • the voltage drops already by more than 10 V in the first 10 hours of operation and then drops further in the first 30 hours of operation.
  • the Figure also shows that -apart from the customary fluctuations-the nipples remain very stable when viewed on a long-term scale, i.e. the electrode gap does not change as significantly any more during the further life span of the lamp as in the first 30 hours of operation.
  • Fig. 6 This is schematically shown in Fig. 6, which only shows the schematic arrangement of the lamp 1 in the reflector 15 without the devices for contacting the supply line of the lamp 1.
  • the reflector 15 has a first focus F 1 .
  • This focus Fi is in the center of the discharge vessel of the lamp 1.
  • the reflector 15 also has a second focus F 2 lying far in front, outside the reflector 15.
  • the focal distance dp is 45 mm here, i.e. far below the customary focal distance of reflectors conventionally used in projection systems.
  • This small focal distance dF has the advantage that the entire optical arrangement of the projection system can be made shorter.
  • Such a projection system 23 is schematically shown in Fig. 9. Starting from the lamp 1, the light is reflected in the reflector 15 onto the second focus F 2 .
  • This focus F 2 is, for example, directly present in a customary color-changing device, for example on a color changer disk 16 which ensures that different colors are produced in a time sequence.
  • DLP Digital Light Processing
  • Such a display device 18 comprises a type of chip on which a plurality of tiny mobile mirrors, one mirror per pixel to be represented, are affixed as individual display elements. These mirrors are illuminated by the light.
  • a pixel at the projection area i.e.
  • the associated mirror is tilted in such a direction that the light is reflected onto the projection area or away from it to an absorber.
  • Any other system may alternatively be used, for example an LCD (Liquid Crystal Display) system, with which a defined reduction of the light is possible.
  • LCD Liquid Crystal Display
  • the most diverse display devices 18 as well as their operation in the projection systems 23 are known to those skilled in the art, as are different color-changing devices.
  • the image is then further projected onto a projection area 20 by an objective lens 19.
  • the lamp 1 is operated by a customary lamp control 21.
  • the entire projection system 23 is controlled by a system control unit 22, which drives the lamp control 21, the color changer 16, the display device 18, and if necessary also the objective lens 19, and particularly arranges for the synchronization of the operation of the lamp 1, the color changer 16, and the display device 18.
  • the outstanding characteristics of the lamp according to the invention in particular the low temperature at the ends of the sealing sections, even render it possible to use reflectors which are closed off by a safety screen in front, without this leading to an overheating of the lamp inside the reflector.
  • a safety screen has the advantage that, in cases in which it comes to a destruction of the lamp after a longer period of operation, no pieces of broken glass can reach other regions of the projector system, but the lamp 1 together with the reflector 15 can be easily replaced by the final user.

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Discharge Lamps And Accessories Thereof (AREA)
  • Discharge Lamp (AREA)

Abstract

L’invention concerne une lampe à décharge (1) de vapeurs de mercure à haute pression comprenant une enveloppe (2) dans un matériau capable de résister aux températures élevées comprenant une cuve de décharge (3) et deux électrodes (5, 6) s’étendant depuis deux sections d’étanchéité (4) dans la cuve de décharge (3), lesdites deux électrodes comprenant un espace inter-électrodes (de) inférieur ou égal à 2,5 mm, de préférence inférieur ou égal à 1,5 mm. La cuve de décharge (3) est remplie pour l’essentiel des substances suivantes : gaz rare, oxygène, halogéné composé de chlore, de brome, d’iode ou d’un mélange de ces éléments ainsi que du mercure dans une quantité égale ou supérieure à 0,15 mg/mm3. Les électrodes (5, 6) sont en forme de tige et sont conçues de telle sorte qu’elles présentent chacune à leur pointe un mamelon (7) qui s’étend dans la direction longitudinale des électrodes (5, 6) après une période de fonctionnement donnée de ces dernières. L’invention concerne également un procédé de fabrication d’une telle lampe à décharge (1) de vapeurs de mercure à haute pression ainsi qu’un système de projecteur pour une telle lampe à décharge (1) de vapeurs de mercure à haute pression.
PCT/IB2006/054974 2006-01-03 2006-12-20 Lampe à décharge de vapeurs de mercure à haute pression et procédé de fabrication d’une lampe à décharge de vapeurs de mercure à haute pression WO2007077504A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP06100048.5 2006-01-03
EP06100048 2006-01-03

Publications (2)

Publication Number Publication Date
WO2007077504A2 true WO2007077504A2 (fr) 2007-07-12
WO2007077504A3 WO2007077504A3 (fr) 2008-05-29

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2006/054974 WO2007077504A2 (fr) 2006-01-03 2006-12-20 Lampe à décharge de vapeurs de mercure à haute pression et procédé de fabrication d’une lampe à décharge de vapeurs de mercure à haute pression

Country Status (2)

Country Link
TW (1) TW200731318A (fr)
WO (1) WO2007077504A2 (fr)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0969353A (ja) * 1995-08-31 1997-03-11 Toshiba Lighting & Technol Corp 高圧放電ランプおよびこれを用いた投光装置並びにプロジェクタ装置
EP0978864A2 (fr) * 1998-08-04 2000-02-09 Stanley Electric Co., Ltd. Lampe à halogénure métallique à double culot à basse puissance
US20020117968A1 (en) * 2000-12-16 2002-08-29 Derra Guenther Hans High-pressure gas discharge lamp, and method of manufacturing same
US6646380B1 (en) * 1999-11-30 2003-11-11 U.S. Philips Corporation High-pressure gas discharge lamp
WO2004055858A2 (fr) * 2002-12-13 2004-07-01 Koninklijke Philips Electronics N.V. Lampe a decharge a pression elevee

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0969353A (ja) * 1995-08-31 1997-03-11 Toshiba Lighting & Technol Corp 高圧放電ランプおよびこれを用いた投光装置並びにプロジェクタ装置
EP0978864A2 (fr) * 1998-08-04 2000-02-09 Stanley Electric Co., Ltd. Lampe à halogénure métallique à double culot à basse puissance
US6646380B1 (en) * 1999-11-30 2003-11-11 U.S. Philips Corporation High-pressure gas discharge lamp
US20020117968A1 (en) * 2000-12-16 2002-08-29 Derra Guenther Hans High-pressure gas discharge lamp, and method of manufacturing same
WO2004055858A2 (fr) * 2002-12-13 2004-07-01 Koninklijke Philips Electronics N.V. Lampe a decharge a pression elevee

Also Published As

Publication number Publication date
WO2007077504A3 (fr) 2008-05-29
TW200731318A (en) 2007-08-16

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