WO2009149973A2

WO2009149973A2 - High-pressure discharge lamp

Info

Publication number: WO2009149973A2
Application number: PCT/EP2009/054455
Authority: WO
Inventors: Michael Beau
Original assignee: Osram Gesellschaft mit beschränkter Haftung
Priority date: 2008-05-28
Filing date: 2009-04-15
Publication date: 2009-12-17
Also published as: WO2009149973A3; DE202008007162U1

Abstract

According to the invention, the ceramic discharge vessel has a bulbous shape with a cylindrical center part and a hemispherical end piece, the filling containing Hg, Xe (0.1 to 3 bar) and metal halides.

Description

Title: High pressure discharge lamp

Technical area

The invention relates to a high-pressure discharge lamp according to the preamble of claim 1. Such lamps are high-pressure discharge lamps with a ceramic discharge vessel, in particular for general lighting.

State of the art

US Pat. No. 5,059,865 discloses a high-pressure discharge lamp in which a metal halide filling together with xenon is used as filling gas for a quartz glass discharge vessel. This lamp type is designed for automotive lamps and represents a combination of xenon high-pressure lamp (for the first few minutes) and metal halide lamp for continuous operation to meet the requirements of a car lamp.

DE 103 12 290, WO 2005/088673 and EP 883 160 use a ceramic discharge vessel with an Hg-free metal halide filling. Xenon is used with at least 1 bar filling pressure. At the same time Na-iodide serves as a metal halide filling.

On the other hand, sodium high-pressure lamps with high xenon pressure are also known, see DE 196 40 850.

Presentation of the invention

The object of the present invention is to provide a metal halide high-pressure discharge lamp for the general purpose provide lighting, with the highest possible light output is achieved.

This object is achieved by the characterizing features of claim 1.

Particularly advantageous embodiments can be found in the dependent claims.

On the one hand, the metal halide lamp according to the invention uses a bulbous geometry of a ceramic discharge vessel, which per se is known per se, see US Pat. No. 5,936,351. This vessel shape avoids cold corners, such as those used in ceramic discharge vessels for high-pressure sodium lamps. The discharge vessel is isothermal, so that the temperature of the cold spot can be increased without overheating the ceramic.

This makes it possible to increase the vapor pressure of NaJ (sodium iodide). The discharge vessel is also designed without massive plugs, because these would lead to increased heat radiation.

The filling contains Hg, so that a better light output and maintenance longer life and easier ignition is achieved than with Hg-free lamps. Ignition only occurs at typical 4.5 kV. In Hg-free lamps, a high xenon filling pressure serves to increase the burning voltage.

On the other hand, with deliberate use of Hg with moderate xenon filling pressure of 0.1 to 3 bar, preferably 0.3 to 0.6 bar, the luminous efficacy can be increased, namely by up to 11 lm / W. In the area of higher filling pressures of about 1 to 3 bar can be achieved particularly high luminous efficiencies, in the range of relatively low filling pressures, the ignition succeeds particularly reliable.

This is essentially due to the fact that the bulbous geometry makes it possible to increase the vapor pressure of the NaJ, which increasingly forms Na-Xe excimers, which can emit light very efficiently. Other iodides are used to improve the color rendering, so that a light source for general lighting is available for the highest demands.

The discharge vessel is typically made of aluminum-containing ceramics such as PCA or YAG, AlN, or A1YO3. The ceramic is preferably doped, as known per se.

The color rendering of such lamps is well above Ra = 80 and the color temperature at typically 2800 to 3100 K.

(warm white) up to 3800 to 4400 K (neutral white). The

Color temperature can be further increased by suitable filling additives. The Na-Xe excimer causes a

Increase in radiant power in the green spectral range.

Brief description of the drawings

In the following, the invention will be explained in more detail with reference to several embodiments. The figures show:

1 shows a high-pressure discharge lamp with discharge vessel;

FIG. 2 shows a discharge vessel in detail; 3 shows a spectrum of the high-pressure discharge lamp with discharge vessel from FIG. 1.

Preferred embodiment of the invention

1 shows schematically a metal halide lamp 1. It consists of a discharge vessel 2 made of ceramic, in which two electrodes 3 are inserted. The discharge vessel has a central part 5 and two ends 4. At the ends sit two seals 6, which are designed here as capillaries. Preferably, the discharge vessel and the seals are made integrally from a material such as PCA, as shown in FIG.

The discharge vessel 2 is surrounded by an outer bulb 7. The discharge vessel 2 is held in the outer bulb by means of a frame 8.

Figure 2 shows an integral discharge vessel 12 in detail with the dimension for the radius R of the half-shell at the ends 4, the straight portion 10 of the length L between the half-shells and the electrode spacing EA.

The ceramic discharge vessel 2 shown in FIG. 2 is intended, for example, for a 70 W lamp. It consists of a cylindrical straight middle part 10 with the length L = 2 mm and two hemispherical end pieces 4 with the radius R = 4 mm. The total length of the inner volume is 10 mm. The wall thickness of the discharge vessel is 0.9 mm in the straight section. The maximum outside diameter is 9, 8 mm. At the end pieces 4 extend axially in each case cylindrical, integral lugs to the outside. They have the function of capillaries 16. In this way an ideal isotherm is produced. In the capillaries, similar to that described in EP-A 587 238, in each case an electrode system is used, the electrode spacing being 7.5 mm. The charge contained in the discharge volume contains Hg, Xe as well as a mixture of the metal halides NaJ and TlJ with rare earth iodides, such as DyJ3, TmJ3 and HoJ3, or CeJ3 as they are usually used for lamps with high wall load. This achieves an initial color temperature of 3030 +/- 80 K in vertical and 2980 +/- 80 K in horizontal burning position. The temperature difference between the cold spot and the hot spot is only 20 ^° C. for this lamp, in contrast to 70 ^° C. for conventional cylindrical lamps with end faces arranged at right angles. The wall load of this discharge vessel is about 28 W / cm ² . The internal volume of the discharge vessel is 370 μl.

It can be displayed neutral white or warm white light colors. In other similarly constructed embodiments, the lamp power is selected higher. At 100 W power, L = 2.5 mm and R = 4.5 mm. At 150 W power, L = 2 mm and R = 6 mm. At 250 W power, depending on the light color, L is typically chosen between L = 2 to L = 6 mm and R typically selected between R = 7.0 mm to R = 9 mm.

A typical ratio of L / R = 0.2 to 0.8. L should preferably be at least 2 mm.

In order to satisfactorily meet the requirements which the contour shown above satisfies, it is also sufficient to approximate the dimensional rules given above with a maximum of 15% deviation.

Therefore, for the limiting case of small lengths of the central part (L approximately equal to 0.5 R), the description of the inner contour by means of an elliptical formula with the Halbach- sen a and b possible because this approximation is accurate to 15%.

Assuming that the small semiaxis a of the ellipse is chosen such that the deviation from the ideal contour (with radius R and length L of the middle part) is at most 15%:

R <a <1, 1 R, and taking into account the fact that the large semiaxis b can be represented as b = R + L / 2, a ratio for the semiaxes of the ellipsoid of: b / a <1.25.

The remaining design rules with regard to electrode spacing and wall load apply unchanged.

A specific embodiment is a 70 W lamp, in which the inner contour 10 of the discharge vessel 9 is formed as a closed ellipsoid having the dimensions a = 4.4 mm and b = 5 mm, starting from a design with R = 4 mm. Thus, b / a = 1.14. The end pieces 11 are integrally made of a single ceramic molding made of alumina. The wall thickness gradually increases from the center, where it is 0.8 mm, to twice the ends. In general, the ceramic discharge vessel should be designed so that the contour of the inner wall of the discharge vessel defines an internal volume V, and that the discharge vessel has a longitudinal axis and two openings with openings, wherein in the ends of electrical feedthroughs are gas-tight, which are electrically connected to two electrodes are, which face each other in the internal volume in a given electrode distance EA, wherein the contour of the inner wall has the following geometry: The contour has a substantially straight cylindrical middle part of length L and inner radius R and two substantially hemispherical end pieces of the same radius R, the length of the cylindrical middle part is smaller or equal to its inner radius:

L <R,

The internal length of the discharge vessel is at least 10% greater than the electrode spacing EA: 2R + L> 1.1 EA,

The diameter (2R) of the discharge vessel must be at least 80% of the electrode spacing EA; at the same time, it may not exceed 150% of the electrode spacing EA: 1.5 EA> R> 0.4 EA.

Table 1 shows a comparison between different fillings for a given discharge vessel. The first filling is conventional with 0.1 bar argon. The second filling contains 0.5 bar xenon instead of the argon and the third filling 1 bar xenon. Indicated are the luminous flux Φ, the efficiency η, and the color temperature tn.

In FIG. 3, the spectrum of a lamp according to pattern 1 is compared with the spectrum of a lamp according to pattern 2. It clearly shows the contribution of the Na-Xe excimer, which causes an increase in the radiation power in the green spectral range (dashed curve).

A typical filling contains 2 to 40 mg Hg. For 250 W power, 8 to 30 mg Hg is used.

Xe: 0.1 to 3 bar,

As metal halides, the filling contains the following constituents:

NaJ: 3 to 70% by weight,

Rare earth od SEJ3, here iodides of Ce, Dy, Tm, Ho alone or in mixture: 3 to 53 wt .-%,

TlJ: 1.2 to 28% by weight,

CaJ 2: 2 to 71% by weight.

Preferably, L is chosen to be less than or equal to 0.75 R. In particular, L> 0.1 R should be chosen.

The inner contour of the discharge vessel can also be described by an ellipsoid of revolution with the semiaxes a and b, where R = a = 1.37 R and b = R + L / 2.

A further advantage lies in the better luminous flux maintenance with xenon filling:

The group Gr 1 of a 250W lamp with neutral white filling was filled with 120 mbar Ar, the group Gr 2 with 380 mbar xenon, see Table 2. There, σ (G) means the Standard deviation of the size G in each case, Δ (G) the difference between the 1000 hours and the 100 hours value of the quantity G, that is Δ (G) = G (1000h) -G (1000h), Q (G ) is the quotient between the 1000 hours and the 100 hours value of size G: G (1000h) / G (100h). At 2500h, there is a higher luminous flux Φ of 25, 6 kirn compared to 23, 6 klm and a better maintenance of 90% compared to 85%. tn is the color temperature, ul is the lamp voltage in volts, uls is the peak erosion voltage in volts, de is the distance to Planck's curve.

Tab. 2

Claims

claims

A high-pressure discharge lamp for general lighting comprising a ceramic discharge vessel surrounding a discharge volume, electrodes extending into the discharge volume enclosed by the discharge vessel, and wherein a filling containing metal halides is accommodated in the discharge volume, the discharge vessel being surrounded by an outer bulb and it is supported therein by a frame, characterized in that the filling contains the following components: Hg: 2 to 40 mg; Xe: 0.1 to 3 bar; NaI: 3 to 70% by weight; SEJ3: 3 to 53% by weight TlJ: 1.2 to 28% by weight;

CaJ2: 2 to 71 wt .-%, wherein also the discharge vessel has the following contour: the contour has a substantially straight cylindrical middle part of length L and the inner radius R and two substantially hemispherical end pieces with the same radius R,

• the length of the cylindrical middle section is smaller or equal to its inner radius:

L <R,

• the inside length of the discharge vessel is at least 10% larger than the electrode distance EA:

2R + L> 1.1 EA,

• The diameter (2R) of the discharge vessel must be at least 80% of the electrode distance EA; at the same time, it may not exceed 150% of the electrode spacing EA:

EA>R> 0.4 EA.

2. High-pressure discharge lamp according to claim 1, characterized in that the wall load of the discharge vessel is between 18 and 45 W / cm ² .

3. High-pressure discharge lamp according to claim 1, characterized in that L ≤ 0.75 R.

4. High-pressure discharge lamp according to claim 1, characterized in that L> 0.1 R.

5. High-pressure discharge lamp according to claim 1, character- ized in that the inner contour is described by an ellipsoid of revolution with the semi-axes a and b, wherein

R <a <1.37 R and b = R + L / 2.