EP2191494B1 - High-pressure discharge lamp with partial coating and vehicle headlight comprising said lamp - Google Patents

Abstract

A high-pressure discharge lamp may include at least one discharge vessel; and two electrodes, which extend into a discharge space of the discharge vessel and between which a light-emitting discharge arc is formed during operation of the high-pressure discharge lamp, wherein a partial coating is applied to a circumferential surface of the lamp in the region of an end section, on the discharge space side, of at least one of the electrodes, said partial coating changing the luminance and color temperature of the emitted light.

Description

Technical area

The invention relates to a high-pressure discharge lamp, in particular for a vehicle headlight, having at least one discharge vessel and two electrodes extending into a discharge space of the discharge vessel, between which forms a light-emitting discharge arc during operation of the high-pressure discharge lamp. The invention further relates to a vehicle headlight provided with at least one such high-pressure discharge lamp.

State of the art

Such a high-pressure discharge lamp is, for example, on the Internet domain www.osram.de described under the product designation "XENARC ^®". These conventional discharge lamps have a discharge vessel delimiting a discharge space filled with an ionizable filling into which two electrodes are connected, which are connected to supply leads led out of the discharge vessel and generate a gas discharge during operation of the lamp which forms a light-emitting discharge arc ,

To improve the ignition properties is for example from the DE 10 2004 043 636 A1 a high-pressure discharge lamp is known in which an electrically conductive, light-transmitting layer as at least partial coating is applied to the surface of the discharge vessel. This coating, together with the electrodes and possibly with the power supply lines, forms a capacitor, with the glass of the discharge vessel in between and the filling gas in the discharge space forming the dielectric of this capacitor. As a result, in particular with the aid of the high-frequency components of the ignition pulse, a dielectrically impeded discharge is produced in the discharge space between the electrodes and the coating. This dielectrically impeded discharge generates a sufficient number of free charge carriers in the discharge space in order to enable the electrical breakdown between the two electrodes of the high-pressure discharge lamp or to considerably reduce the ignition voltage required for this purpose.

A disadvantage of such high-pressure discharge lamps is that the color temperature and luminance of the discharge arc over the length of the discharge arc is formed unevenly, so that light emitted by the lamp, especially when using such high-pressure discharge lamps in vehicle headlights, can lead to dazzling other road users. In particular, so-called hot spots in the discharge space of such lamps, which have an extremely high color temperature, lead to dazzling of oncoming vehicles.

The US 2004/174121 A1 . US 2005/116608 A1 . DE 102 47 983 A1 and EP 0 682 356 A2 each disclose the luminance and color temperature-changing coatings on lamp vessels.

Presentation of the invention

The invention has for its object to provide a high-pressure discharge lamp and a vehicle headlamp with at least one such high-pressure discharge lamp, in which compared to conventional solutions an improved lighting effect is possible.

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

Due to the inventive coating of the high-pressure discharge lamp in the region of a discharge space-side end portion of at least one electrode is achieved that the lamp color and luminous homogeneous and other road users, for example oncoming motorists no longer or at least less dazzling, since the luminance as well as the color temperature by such a partial coating is changed. Furthermore, by such a partial coating, the geometry of the actual luminous body can be set very accurately. As a result, for example, the reflector geometry of a headlight can be adapted much better to the discharge lamp, so that an improved lighting effect is achieved.

According to a particularly preferred embodiment of the invention, the partial coating is formed as the luminance and color temperature of the emitted light degrading coating.

For safety reasons, the discharge vessel of the lamp is surrounded at least in sections by an outer bulb in a preferred embodiment of the invention. In this case, it is possible for the coating to be applied on the outer peripheral surface of the outer bulb and / or on the outer peripheral surface of the discharge vessel. A coating applied to the outer peripheral surface of the outer bulb is thermally less stressed than a coating which is applied to the discharge vessel. The application of the coating on the outer surface of the discharge vessel has the advantage that the coating is protected against mechanical damage and unwanted reactions of the coating can be prevented by means provided in the space of outer bulb and discharge vessel gas filling, in particular an inert gas. However, the invention is not limited to such lamp types with outer bulb, but the high-pressure discharge lamp can be formed without an outer bulb having applied to the discharge vessel coating.

Preferably, a coating is applied in each case to a coating on the peripheral surface of the outer bulb and / or of the discharge vessel in the region of the discharge-space-side end sections of both electrodes.

In an embodiment according to the invention of the high-pressure discharge lamp, the coating is applied at least to a circumferential section of the outer bulb and / or of the discharge vessel.

It has proved to be particularly advantageous if the coating extends annularly around the outer bulb and / or the discharge vessel. The coating forms an annular cover of the very bright, white hot spots with high color temperature, so that the light effect of the lamp is color and light homogeneous.

In one embodiment of the high-pressure discharge lamp according to the invention, the coating is applied to the outer bulb or the discharge vessel such that it encompasses the end portion of the electrode at a distance. It has proven to be particularly advantageous if the coating is applied in each case beginning approximately 0.2 to 1.2 mm, preferably 0.5 mm in front of the discharge space-side end portion of the electrode and extending in the direction of an end portion of the discharge vessel. The coating preferably extends in each case from the discharge space at least to a melting of the electrode in the discharge vessel of the high-pressure discharge lamp.

In an alternative embodiment of the invention, the coating is applied in each case from one end of the electrode starting on the outer bulb or the discharge vessel and extends in the direction of the end portions of the discharge vessel. In this variant At least a portion of the radiation emitted in the region of the ends of the electrodes is not detected by the coating, so that a very high luminance is achieved.

In order to influence the position and geometry of the coating, this is preferably applied in mask or glare technique.

A coating according to the invention preferably has at least one absorption filter, an interference filter and / or a combination of such filters. Depending on the design of the coating, absorption or partial absorption of the light emitted by the discharge arc can be achieved. With an interference filter arrangement, it is possible in particular to filter light in an undesired wavelength range causing a glare from the emission spectrum of the discharge lamp.

In one embodiment of the invention, the coating is applied to the outer bulb and / or the discharge vessel by means of a vacuum coating method. In the vacuum coating process, a coating with a defined layer thickness and high adhesion is achieved. It is advantageous that the vacuum coating process is continuous, ie no intermediate ventilation of the vacuum chamber takes place and thereby no contamination of the coating occur, so that the quality of the coating of the high-pressure discharge lamp is substantially improved. The optical properties of the coating can be easily be adjusted by the material used, the layer geometry and thickness of the layer to achieve the desired improvements in the lighting effect. The coating may consist of one or more materials.

In a particularly preferred embodiment of the invention, the coating is applied in PVD sputtering or CVD technology. For example, a reactive PVD sputtering process is used.

In particular, in a high-pressure discharge lamp used in a vehicle headlight, the uncoated portion of the outer peripheral surface of the outer bulb or of the discharge vessel preferably has a sufficiently high luminance in order to achieve the required illuminance according to ECE standard.

Brief description of the drawings

• Figur 1 eine schematische Darstellung einer erfindungsgemäßen Hochdruckentladungslampe und
• Figur 2 eine schematische Darstellung der Hochdruckentladungslampe aus Figur 1 im Bereich des Entladungsraumes mit Entladungsbogen.

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

• FIG. 1 a schematic representation of a high-pressure discharge lamp according to the invention and
• FIG. 2 a schematic representation of the high pressure discharge lamp FIG. 1 in the region of the discharge space with discharge arc.

Preferred embodiment of the invention

The invention will be explained below with reference to a high-pressure discharge lamp, as used for example in vehicle headlights. However, the high-pressure discharge lamp according to the invention is by no means limited to such lamp types.

FIG. 1 shows a schematic representation of a high-pressure discharge lamp 1 with a discharge vessel 2 (burner) made of quartz glass which delimits a discharge space 4 and two diametrically arranged, sealed end sections 6, 8 in which a molybdenum foil 10 is embedded for gas-tight electrical feedthrough. The molybdenum foils 10 are connected at a first narrow side 12 to an outer power supply 14, 16 made of doped molybdenum. In the discharge space 4 of the discharge vessel 2 protrude two diametrically arranged electrodes 18, 20 of doped tungsten, which are each connected to a second narrow side 22 of the molybdenum foils 10 and between which forms a light-emitting gas discharge during lamp operation. In the discharge space 4 of the discharge vessel 2, an ionizable filling is included, which consists of high-purity xenon gas and a plurality of metal halides. The discharge vessel 2 is surrounded by an outer bulb 24, which consists of quartz glass, which is provided with ultraviolet radiation absorbing dopants. The high-pressure discharge lamp 1 also has a lamp cap 26, which carries the discharge vessel 2 and the outer bulb 24. The lamp base 26 has a partially cylindrical base housing 28 made of electrically insulating plastic for receiving in a lamp holder, not shown, the lamp side has a mounting portion 30 with a fixing ring 32 for fixing the outer bulb 24 in the base housing 28. The outer power supply 14 of the socket-distal end portion 6 of the discharge vessel 2 is connected via an insulating sleeve 34 surrounded current return 36 with an electrical connection ring 38 of the base 26, while the sockelnahe power supply 16 is connected to an inner contact pin, not shown, of the high-pressure discharge lamp 1.

On an outer peripheral surface 40 of the outer bulb 24, in the region of a discharge-space-side end portion 42, each of the electrodes 18, 20 has a partial coating 44 which modifies the luminance and color temperature of the emitted light. The coatings 44 are each approximately annularly applied to the outer bulb 24 such that they surround the end portions 42 of the electrodes 18, 20 spaced apart and extend to a melting 48 of the electrodes 6, 8 in the discharge vessel 2. Due to the coatings 44 of the high-pressure discharge lamp 1 according to the invention, it is achieved that the lamp appears colorless and luminous more homogeneous and no longer or at least less dazzling to other road users, for example oncoming motorists, since the luminance as well as the color temperature is lowered by such a partial coating 44. Furthermore, by such a partial coating 44, the geometry of the actual luminous body can be set very accurately. As a result, for example, the reflector geometry a headlamp much better adapted to the discharge lamp 1, so that an improved lighting effect is achieved. The attachment of the coating 44 on the outer peripheral surface 40 of the outer bulb 24 is compared with a coating which is applied to the discharge vessel 2 thermally less burdened. An uncoated portion 46 of the outer peripheral surface 40 of the outer envelope 24 has a sufficiently high luminance to achieve the illuminance required for street illumination by the ECE.

In an embodiment of the invention, not shown, the coating 44 is applied to the discharge vessel 2. The application of the coating 44 on the outer peripheral surface of the discharge vessel 2 has the advantage that the coating 44 is protected against mechanical damage and undesirable reactions of the coating can be prevented by means of a gas filling provided in the space between the outer bulb and the discharge vessel, in particular an inert gas filling. Furthermore, the coating 44 may each be applied from one end of the electrodes 18, 20 starting on the outer bulb 24 or the discharge vessel 2 and extending in the direction of the end portions 6, 8 of the discharge vessel 2.

The coating 44 has at least one absorption filter, an interference filter and / or a combination of such filters and, in the exemplary embodiment shown, is applied to the outer bulb 24 by means of a vacuum coating method. In order to influence the position and geometry of the coating 44 is these applied, for example, in mask or glare technique. In the vacuum coating process, a coating with a defined layer thickness and high adhesion is achieved. It is advantageous that the vacuum coating process is continuous, ie no intermediate ventilation of the vacuum chamber takes place and thereby no contamination of the coating occur, so that the quality of the coating of the high-pressure discharge lamp 1 is substantially improved. The optical properties of the coating 44 can be readily adjusted by the material used, the layer geometry and the thickness of the layer to achieve the desired improvements in luminous efficiency. The coating can consist of different materials. For example, the coating can be applied in PVD sputtering or CVD technology.

According to FIG. 2 showing a detailed view of the high-pressure discharge lamp 1 FIG. 1 In the illustrated embodiment, the coating 44 in the illustrated embodiment extends in each case from a distance X of approximately 0.2 to 1.2 mm, preferably 0.5 mm, in front of the discharge-space-side end sections 42 of the electrodes 18 in the region of the discharge space 4 , 20 starting in the direction of the end sections 6, 8 of the discharge vessel 2 (see FIG. 1 ). In this case, the coating 44 forms an annular covering of the very bright, white hot spots 52 having a high color temperature occurring in the edge region of the electrodes 18, 20, so that the light effect of the lamp is color and luminous more homogeneous. The arc length L is in the illustrated embodiment of the invention about 5 mm. A central Area 54 of the discharge arc 50 having the width T has at least about 50% of the maximum luminance. A portion 56 of the discharge arc 50 having a width T is characterized by a luminance of at least about 20% of the maximum luminance, wherein a center 58 of the luminance is spaced a distance R from a reference axis 60.

The high-pressure discharge lamp 1 according to the invention is not limited to lamps with outer bulb 24, but the high-pressure discharge lamp can be embodied without an outer bulb 24 with coating 44 applied to the discharge vessel 2. Furthermore, the geometry of the coating 44 is not limited to the aforementioned embodiment. In particular, the coating 44 may be applied only to one or more peripheral portions of the outer bulb 24 or the discharge vessel 2.

Disclosed is a high-pressure discharge lamp 1, in particular for a vehicle headlight, with at least one discharge vessel 2 and two extending into a discharge space 4 of the discharge vessel 2 electrodes 18, 20, between which forms a light-emitting discharge arc 50 during operation of the high-pressure discharge lamp 1, wherein on a Peripheral surface 40 of the lamp in the region of a discharge-space-side end portion 42 of at least one of the electrodes 18, 20 a the luminance and color temperature of the emitted light changing partial coating 44 is applied. Further disclosed is a vehicle headlamp with at least one such high-pressure discharge lamp.

LIST OF REFERENCE NUMBERS

1

High pressure discharge lamp

2

discharge vessel

4

discharge space

6

end

8th

end

10

molybdenum foil

12

narrow side

14

power supply

16

power supply

18

electrode

20

electrode

22

narrow side

24

outer envelope

26

lamp base

28

housings

30

attachment section

32

fixing

34

insulating sleeve

36

Current feedback

38

Attachment ring

40

Outer circumferential surface

42

end

44

coating

46

section

48

melting

50

discharge arc

52

Hot-Spot

54

Area

56

section

58

center

60

reference axis

Claims (15)

1. High-pressure discharge lamp having at least one discharge vessel (2) and two electrodes (18, 20), which extend into a discharge space (4) of the discharge vessel (2) and between which a light-emitting discharge arc (50) is formed during operation of the high-pressure discharge lamp (1), wherein a partial coating (44) is applied to a circumferential surface (40) of the lamp in the region of an end section (42), on the discharge space side, of at least one of the electrodes (18, 20), said partial coating (44) changing the luminance and color temperature of the emitted light, characterized in that the coating (44) is applied beginning approximately 0.2 to 1.2 mm in front of the end section (42), on the discharge space side, of the electrode (18, 20), and extends in the direction of an end section (6, 8) of the discharge vessel (2).
2. High-pressure discharge lamp according to Claim 1, wherein the coating (44) reduces the luminance and color temperature of the emitted light.
3. High-pressure discharge lamp according to Claim 1 or 2, wherein at least sections of the discharge vessel (2) are surrounded by an outer bulb (24).
4. High-pressure discharge lamp according to Claim 3, wherein the coating (44) is applied to the circumferential surface, in particular the outer circumferential surface (40) of the outer bulb (24).
5. High-pressure discharge lamp according to one of Claims 1 to 3, wherein the coating (44) is supplied to an outer circumferential surface of the discharge vessel (2).
6. High-pressure discharge lamp according to one of the preceding claims, wherein in each case one coating (44) is applied in the region of the end sections (42) on the discharge space side of the two electrodes (18, 20).
7. High-pressure discharge lamp according to one of the preceding claims, wherein the at least one coating (44) extends at least around a circumferential section of the outer bulb (24) or the discharge vessel (2).
8. High-pressure discharge lamp according to one of the preceding claims, wherein the at least one coating (44) extends approximately in annular fashion around the outer bulb (24) or the discharge vessel (2).
9. High-pressure discharge lamp according to one of the preceding claims, wherein the at least one coating (44) engages around the end section (42) of the electrode (18, 20) at a distance.
10. High-pressure discharge lamp according to one of the preceding claims, wherein the coating (44) extends from the discharge space (4) at least as far as a fuse seal (48) of the electrode (18, 20).
11. High-pressure discharge lamp according to one of the preceding claims, wherein the coating (44) has at least an absorption filter, an interference filter and/or a combination of such filters.
12. High-pressure discharge lamp according to one of the preceding claims, wherein the coating (44) is applied by means of a vacuum coating method.
13. High-pressure discharge lamp according to one of the preceding claims, wherein the coating (44) is applied using the PVD sputtering technique or CVD technique.
14. High-pressure discharge lamp according to one of the preceding claims, wherein the coating is applied using the mask or screen technique.
15. Vehicle headlamp with at least one high-pressure discharge lamp (1) according to one of the preceding claims.

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