EP2499657B1 - Mercury-free high-pressure discharge lamp with a reduced amount of zinc halide - Google Patents

Description

The invention relates to a high-pressure discharge lamp according to the preamble of patent claim 1.

I. State of the art

Such a high-pressure discharge lamp is for example in the US 2009/200944 A disclosed. This document describes a high-pressure discharge lamp for vehicle headlights with eg ("arc tube group 3-2" in Fig. 4 and 7 and the associated description in [0050] ff) a volume of the discharge space of 0.0187 cm ³ , a halide concentration (iodide density ) of 10.7 mg / cm ³ , a zinc halide content of 9%, thus 0.96 mg / cm ^{3 of} the discharge space volume, and a cold fill pressure of xenon of 177 megapascals (17.5 atm.

Similar high-pressure discharge lamps with mercury-free fillings of at least xenon, NaI, ScI3, and ZnI2 are known from the patents WO 2008/122912 A . DE 10 2007 018614 A . WO 2009/127993 A . WO 2009/040709 A , such as EP 2 086 001 A known.

Another high pressure discharge lamp for vehicle headlights is in the EP 1 351 276 A2 disclosed; with a mercury-free filling having a zinc iodide content in the range of 2 mg to 6 mg per 1 cm ^{3 of} the discharge vessel volume.

The patent US Pat. No. 7,126,281 B1 describes a high pressure discharge lamp for vehicle headlights with an electrical power consumption of about 35 watts and a mercury-free filling containing xenon and halides of the metals sodium, scandium, indium and zinc.

The US 2008/001543 A1 discloses a mercury-free metal halide high pressure discharge lamp whose fill contains a halide of thulium.

The zinc component of the filling replaces the mercury used earlier and is needed to adjust the so-called burning voltage of the high-pressure discharge lamp. The term firing voltage refers to the operating voltage of the high-pressure discharge lamp after completion of its ignition and start-up phase and the achievement of its quasi-steady-state operating state in which all filling components are present in the gaseous state. However, the use of the zinc component in the filling has the disadvantage that the luminous flux generated by the high-pressure discharge lamp decreases with increasing zinc content in the filling.

II. Presentation of the invention

It is an object of the invention to provide a generic high-pressure discharge lamp, which does not have the aforementioned disadvantage. In particular, a high-pressure discharge lamp with a mercury-free filling is to be provided, which has a reduced compared to the above-cited prior art electrical power consumption and a comparable burning voltage and generates a sufficiently high for use as a light source in the vehicle headlights luminous flux.

This object is achieved by a high-pressure discharge lamp with the features of claim 1. Particularly advantageous embodiments of the invention are described in the dependent claims.

The high-pressure discharge lamp according to the invention is provided as a light source in headlights of motor vehicles and has a discharge chamber sealed in a gastight manner, in which electrodes and a filling for generating a gas discharge are enclosed, wherein the filling is formed as a mercury-free filling, the at least xenon and halides of sodium , Scandium, and zinc. The filling is formed as a zinc reduced filling having a zinc halide content in the range of greater than 0 mg to 1.0 mg per 1 cm ^{3 of} the discharge space volume, the amount of halides in the discharge space is in the range of 8 mg to 15 mg per 1 cm ^{3 of} the Discharge space volume, the cold pressure of xenon (which is the pressure of the xenon in the discharge space, measured at a temperature of 25 degrees Celsius) is in the range of 1.0 megapascal to 1.8 megapascals and the volume of the discharge space has a value in the range of 0.015 cm ³ to 0.022 cm ³ . The term mercury-free filling means that neither mercury nor a mercury compound is introduced into the discharge space of the discharge vessel.

In addition, the filling of the high-pressure discharge lamp according to the invention contains thulium in the form of thulium halide for adjusting the burning voltage, the content of thulium halide in the filling being in the range from 10% to 30% by weight of the halides.

Here, the effect of thulium is similar to that of zinc, namely the increase of the burning voltage, the decrease of the luminous flux with increasing Thuliumanteil is not as strong as the zinc.

By the aforementioned features, a high-pressure discharge lamp is made possible according to the invention, which has a reduced electrical power consumption at comparable burning voltage compared to the high-pressure discharge lamp according to the prior art and generates a sufficiently high luminous flux, so that it is suitable as a light source in headlights of motor vehicles. In particular, by reducing the zinc and halides of the zinc in the filling, a high luminous flux can be achieved. The comparatively high filling pressure of the xenon, together with the small volume of the discharge space and the metering of the metal halides, contribute to a sufficiently high burning voltage of the high-pressure discharge lamp, so that the addition of mercury or mercury compounds for filling the high-pressure discharge lamp according to the invention for the purpose of setting its burning voltage can be dispensed with ,

Advantageously, the proportion of zinc halide in the filling in the range of 0.1 mg to 1.0 mg per 1 cm ^{3 of} the discharge space volume in order to ensure a sufficiently high burning voltage and luminous flux of the high-pressure discharge lamp. In FIG. 3 is schematic the relationship between the proportion of zinc halide in percent by weight of the amount of halide in the discharge space and the luminous flux of the high-pressure discharge lamp (curve 1) and the burning voltage of the high-pressure discharge lamp (curve 2). On the horizontal axis is plotted the percentage of zinc halide in weight percent based on the total amount of halides in the filling. On the vertical axis is on the one hand (left side of the Fig. 3 ) the luminous flux of the high pressure discharge lamp in lumens and on the other hand (right side of Fig. 3 ) plotted the burning voltage of the high-pressure discharge lamp in volts. Curve 1 (solid line) shows the dependence of the luminous flux of the high-pressure discharge lamp on the zinc halide content in the filling, while curve 2 (dashed line) illustrates the dependency of the burning voltage of the high-pressure discharge lamp on the zinc halide content in the filling. From the curves 1 and 2 it is clear that with increasing proportion of zinc halide, the burning voltage of the high-pressure discharge lamp increases and the luminous flux decreases.

Advantageously, the filling of the high-pressure discharge lamp according to the invention additionally contains indium halide, wherein the proportion of indium halide in the filling is less than or equal to 3.0 percent by weight of the total amount of halides and thus significantly lower than the proportion of sodium and scandium halide in the filling. The small indium halide content in the filling serves to adjust the color locus of the white light emitted by the high-pressure discharge lamp in the standard color chart according to CIE 1931 and DIN 5033. By means of the comparatively low Indiumhalogenidanteils in the filling ensures that the high-pressure discharge lamp according to the invention generates white light according to the standard ECE Rule 99. A higher indium halide content would adversely affect the luminous flux of the high pressure discharge lamp.

Advantageously, the content of sodium halide in the filling ranges from 30% to 50% by weight of the total amount of halides and the content of scandium halide in the filling ranges from 30% to 60% by weight of the total amount of halides to white light according to ECE Rule 99 with a color temperature in the range of 4000 Kelvin to 4500 Kelvin to produce.

Advantageously, the proportion of zinc halide in the charge is less than or equal to 6 percent by weight based on the total amount of halides. This allows a sufficiently high operating voltage (40V) to be set without the luminous flux being too low due to the addition of zinc.

und vorzugsweise sogar die Beziehung $$1,2\le D1/D2<1,3$$

gilt, worin D1 die Wandstärke des Entladungsgefäßes im Bereich zwischen den Elektroden und D2 die Wandstärke des Entladungsgefäßes in den Endabschnitten des Entladungsraums, in denen die Elektroden angeordnet sind, bezeichnet.The discharge vessel of the high-pressure discharge lamp according to the invention advantageously has an ellipsoidal outer contour in the region of the discharge space and a circular-cylindrical inner contour in the region between the electrodes, wherein the relationship between the wall thickness of the discharge vessel $$1.0\le D1/D2<1.4$$

and preferably even the relationship $$1.2\le D1/D2<1.3$$

is where D1 denotes the wall thickness of the discharge vessel in the region between the electrodes and D2 the wall thickness of the discharge vessel in the end portions of the discharge space in which the electrodes are arranged.

Due to the aforementioned wall thickness ratio, the discharge vessel of the high-pressure discharge lamp according to the invention has a lower convex curvature than the discharge vessel of high-pressure discharge lamps according to the prior art. Therefore, in the case of the high-pressure discharge lamp according to the invention, for example, the optical or optically effective electrode spacing of 4.2 mm prescribed in accordance with ECE Rule 99 can be achieved with the aid of a comparatively larger actual electrode spacing (measured by means of X-ray exposure) than with high-pressure discharge lamps according to the prior art. For example, in the high pressure discharge lamps according to the prior art, the actual electrode spacing is 3.6 mm, while the real electrode spacing in the high-pressure discharge lamps according to the invention is preferably in the range of 3.8 mm to 4.0 mm. The comparatively larger electrode spacing also contributes to a higher burning voltage of the high-pressure discharge lamp according to the invention, so that a sufficiently high burning voltage can be achieved even for this reason, despite the reduction of the amount of zinc component and the absence of mercury in the filling.

Preferably, the discharge vessel in the region between the electrodes has an inner diameter in the range of 2.0 mm to 2.7 mm, more preferably in the range of 2.1 mm and 2.4 mm, and an outer diameter in the range of 5.0 mm and 6.0 mm, more preferably in the range of 5.3 mm and 5.7 mm. As a result, the discharge vessel in the region between the electrodes has a comparatively high wall thickness, which contributes to improved burst protection and good thermal insulation of the discharge vessel.

The electrodes of the high-pressure discharge lamp according to the invention are preferably rod-shaped and have a diameter which is preferably in the range of 0.20 mm to 0.30 mm and particularly preferably in the range of 0.25 mm to 0.27 mm in order to ensure a high current carrying capacity of To ensure electrodes so that the high-pressure discharge lamp according to the invention during the so-called start-up phase, which immediately follows the ignition phase and during which evaporate the halides of the filling, can be operated with three to five times the value of the rated power and thereby faster

Transition can be achieved in the quasi-stationary operating state of the high-pressure discharge lamp.

As already mentioned above, the cold filling pressure of xenon in the filling of the high-pressure discharge lamp according to the invention is in the range from 1.0 megapascal to 1.8 megapascal. However, the range of 1.5 megapascals to 1.7 megapascals is particularly preferred because the burning voltage of the high-pressure discharge lamp according to the invention can be increased by the comparatively high xenon pressure and white light can already be generated by means of the high xenon pressure immediately after the ignition of the high-pressure discharge lamp.

The amount of halides in the interior of the discharge vessel of the high-pressure discharge lamp according to the invention is in the range of 8 milligrams to 15 milligrams per 1 cubic centimeter of the discharge space volume and the discharge space volume has a value in the range of 0.015 cubic centimeters to 0.022 cubic centimeters, as already mentioned above. Particularly preferred is a halide amount in the range of 10 milligrams to 14 milligrams per cubic centimeter of the discharge space volume and a discharge space volume in the range of 0.016 cubic centimeters to 0.019 cubic centimeters for the high pressure discharge lamp of the invention to provide an electrical power consumption in the range of 22 watts to 28 watts in the quasi steady state operating condition To enable high pressure discharge lamp according to the invention.

The high-pressure discharge lamp according to the invention can be designed such that during its operation a Luminous flux of less than or equal to 2000 lm generated in order to use the high-pressure discharge lamp according to the invention in vehicle headlights, which have no headlight washer.

III. Description of the Preferred Embodiment

Figur 1

Eine Seitenansicht einer Hochdruckentladungslampe gemäß dem bevorzugten Ausführungsbeispiel der Erfindung in schematischer Darstellung

Figur 2

Eine vergrößerte Darstellung des Entladungsraums des Entladungsgefäßes, der in Figur 1 abgebildeten Hochdruckentladungslampe in schematischer und geschnittener Darstellung

Figur 3

Eine Darstellung der Abhängigkeit des Lichtstroms und der Brennspannung der Hochdruckentladungslampe von dem Zinkhalogenidanteil in der Füllung

The invention will be explained in more detail below with reference to a preferred embodiment. Show it:

FIG. 1

A side view of a high-pressure discharge lamp according to the preferred embodiment of the invention in a schematic representation

FIG. 2

An enlarged view of the discharge space of the discharge vessel, the in FIG. 1 pictured high pressure discharge lamp in a schematic and sectional view

FIG. 3

A representation of the dependence of the luminous flux and the burning voltage of the high pressure discharge lamp of the zinc halide content in the filling

worin D1 die Wandstärke des Entladungsgefäßes 10 im Bereich zwischen den Elektroden 11, 12 und D2 die Wandstärke des Entladungsgefäßes 10 in den Endabschnitten des Entladungsraums 106, in denen die Elektroden 11, 12 angeordnet sind, bezeichnet.In the preferred embodiment of the invention is a mercury-free metal halide high-pressure discharge lamp with an electrical power consumption of 25 watts. This lamp is intended for use in a vehicle headlight. It has a two-sided sealed discharge vessel 10 made of quartz glass with a volume of the discharge space 106 of 17 mm ³ , in which an ionizable filling is enclosed gas-tight. In the area of the discharge space 106, the outer contour of the discharge vessel 10 is ellipsoidal in shape and its inner contour is circular-cylindrical in the region between the electrodes 11, 12 ( Fig. 2 ). The wall of the discharge vessel 10 is thus convexly curved in the region of the discharge space 106 and has a greater wall thickness between the electrodes 11, 12 than at the two ends of the discharge space 106, in which the electrodes 11, 12 are arranged. The ratio of the wall thicknesses D1 / D2 is in the range of 1.2 to 1.3. That is, it applies the relationship $$1.2\le D1/D2\le 1.3$$

wherein D1, the wall thickness of the discharge vessel 10 in the region between the electrodes 11, 12 and D2, the wall thickness of the discharge vessel 10 in the end portions of the discharge space 106, in which the electrodes 11, 12 are arranged.

In the middle of the discharge space 106, the inner diameter of the discharge vessel is 2.2 mm and its outer diameter is 5.5 mm there. The two ends 101, 102 of the discharge vessel 10 are each sealed by means of a molybdenum foil sealing 103, 104. The molybdenum foils 103, 104 each have a length of 7.5 mm, a width of 2 mm and a thickness of 25 microns. In the interior of the discharge vessel 10 are two electrodes 11, 12, between which forms during the lamp operation responsible for the light emission discharge arc. The electrodes 11, 12 are made of tungsten. Their thickness or their diameter is 0.26 mm. The length of the electrodes 11, 12 is in each case 6.5 mm. The real, that is, measured by means of X-ray recording distance between the electrodes 11, 12 is 3.7 mm, while the optical or optically effective distance between the electrodes 11, 12 is about 3.9 mm. This difference between the real and the optical distance of the electrodes 11, 12 is caused by the optical properties (for example, by the convex curvature and the optical refractive index) of the wall of the discharge vessel 10 in the region of the discharge space 106. The electrodes 11, 12 are in each case electrically conductively connected to one of the molybdenum foil melts 103, 104 and via the base-remote power supply 13 and the current return 17 or via the socket-side power supply 14 to an electrical connection of the lamp base 15 which consists essentially of plastic. The discharge vessel 10 is enveloped by a glass outer bulb 16. The outer bulb 16 has an extension 161 anchored in the base 15. The discharge vessel 10 has a tube-like extension 105 made of quartz glass on the base side, in which the base-side current supply 14 extends.

The current return 17 facing surface region of the discharge vessel 10 is provided with a transparent, electrically conductive coating 107. This coating 107 extends in the longitudinal direction of the lamp over the entire length of the discharge space 106 and over a part, about 50 percent, of the length of the sealed ends 101, 102 of the discharge vessel 10. The coating 107 is mounted on the outside of the discharge vessel 10 and covers about 5 percent to 10 percent of the circumference of the discharge vessel 10. The coating 107 may also extend over 50 percent of the circumference of the discharge vessel 10 or even over more than 50 percent of the circumference of the discharge vessel 10. Such a wide configuration of the coating 107 has the advantage of increasing the efficiency of the high pressure discharge lamp, as it reflects a portion of the infrared radiation generated by the discharge back into the discharge vessel and thereby for selective heating of the colder areas below the electrodes during lamp operation of the discharge vessel 10, in which collect the metal halides of the ionizable filling. The coating 107 consists of doped tin oxide, for example of tin oxide doped with fluorine or antimony or, for example, boron and / or lithium doped tin oxide. This high-pressure discharge lamp is operated in a horizontal position, that is, with arranged in a horizontal plane electrodes 11, 12, wherein the lamp is oriented such that the current return path 17 extends below the discharge vessel 30 and the outer bulb 16. Details of this, acting as a priming coating 107 are in the EP 1 632 985 A1 described. The outer bulb 16 is made of quartz glass doped with ultraviolet ray absorbing materials such as cerium oxide and titanium oxide. Suitable glass compositions for the outer envelope are in the EP 0 700 579 B1 disclosed.

According to an example which does not form part of the invention, the ionizable filling enclosed in the discharge vessel consists of xenon with a cold filling pressure which means a measured at a temperature of 25 ° C filling pressure, of 1.6 megapascals, and the iodides of sodium, scandium, zinc and indium. The burning voltage of the lamp is about 40 volts. Its color temperature is around 4500 Kelvin. The total amount of the halides or iodides of the metals sodium, scandium, zinc and indium in the filling is 13.83 mg / cm ³ , that is 13.83 milligrams per 1 cubic centimeter of discharge space volume, wherein the weight proportions of the iodides of the metals sodium, scandium , Zinc and indium based on the total amount of halides are as follows: sodium: 43.4% by weight, corresponding to a capacity of 6 mg / cm ³ scandium: 50.6 weight percent, corresponding to a capacity of 7 mg / cm ³ iodide: 5.8% by weight, corresponding to a capacity of 0.8 mg / cm ³ indium: 0.2 weight percent, corresponding to a capacity of 0.03 mg / cm ³

This corresponds to a molar sodium to scandium ratio of 2.5: 1. The color rendering index of the metal halide high pressure discharge lamp is 65 and its luminous efficacy is 90 lm / W. The wall load is about 80 W / cm ² . The high-pressure discharge lamp generates a luminous flux of less than or equal to 2000 Im and can therefore be operated in vehicle headlamps without headlight washer, for example, to generate a daytime running light, fog light or continuous running light.

The metal halide high-pressure discharge lamp is operated immediately after the ignition of the gas discharge in the discharge vessel at three to five times its rated power or rated current, in order to ensure rapid evaporation of the metal halides in the ionizable filling. Immediately after the ignition of the gas discharge, it is almost exclusively carried by the xenon, since only the xenon is present in gaseous form in the discharge vessel at this time. The high-pressure discharge lamp operates at this time and during the so-called start-up phase, during which the metal halides of the ionizable filling in the vapor phase, so like a high-pressure xenon discharge lamp, in which both the light emission and the electrical properties of the discharge, in particular the voltage drop across the Discharge range, to be determined solely by the xenon and the electrode distance. Only when the above-mentioned iodides of the ionizable filling are vaporized and they participate in the discharge, a quasi-stationary operating state of the lamp is reached, in which the lamp is operated with its rated power of 25 watts and a burning voltage of 40 volts. The term burning voltage therefore refers to the operating voltage of the high-pressure discharge lamp in quasi-stationary operation.

The filling of the high-pressure discharge lamp according to the invention also contains 10-30 weight percent thulium iodide in addition to the iodides of the metals sodium, scandium, zinc and, for example, indium.

Furthermore, instead of iodides of the aforementioned metals or In addition to the iodides of these metals, other halides, for example, bromides or chlorides of these metals in the filling can be used.

Claims (6)

1. High-pressure discharge lamp for vehicle headlights comprising a discharge vessel (10), which is sealed in a gastight manner and which has a discharge space (106), in which electrodes (11, 12) and a fill for generating a gas discharge are enclosed, wherein the fill is embodied as a mercury-free fill containing at least xenon and halides of sodium, scandium and zinc, wherein
   the quantity of halides present in the discharge space (106) of the discharge vessel (10) is in the range of 8 mg to 15 mg per 1 cm³ of the volume of the discharge space, wherein
   the cold filling pressure of xenon is in the range of 1.0 megapascal to 1.8 megapascals, and
   the volume of the discharge space (106) of the discharge vessel (10) has a value in the range of 0.015 cm³ to 0.022 cm³, wherein the fill has a zinc halide proportion in the range of greater than 0 mg to 1 mg per 1 cm³ of the volume of the discharge space,
   characterized in that
   the fill additionally contains thulium halide, wherein the proportion of thulium halide in the fill is in the range of 10 per cent by weight to 30 per cent by weight of the total quantity of halides.
2. High-pressure discharge lamp according to Claim 1, wherein the fill additionally contains indium halide, and the proportion of indium halide in the fill is less than or equal to 3.0 per cent by weight of the quantity of halides.
3. High-pressure discharge lamp according to Claim 1 or 2, wherein the proportion of sodium halide in the fill is in the range of 30 per cent by weight to 50 per cent by weight of the total quantity of halides.
4. High-pressure discharge lamp according to any of Claims 1 to 3, wherein the proportion of scandium halide in the fill is in the range of 30 per cent by weight to 60 per cent by weight of the total quantity of halides.
5. High-pressure discharge lamp according to any of Claims 1 to 4, wherein the quantity of halides in the discharge space (106) of the discharge vessel (10) is in the range of 10 mg to 14 mg per 1 cm³ of the volume of the discharge space.
6. High-pressure discharge lamp according to any of Claims 1 to 5, wherein the cold filling pressure of xenon is in the range of 1.6 megapascals to 1.8 megapascals.

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