JPH1167156A - Extra high pressure mercury discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the lifetime, while preventing the generation of a leak and a burst of an arc tube due to the generation of crack at the time of lighting and extinguishing a lamp by forming a high-melting point metal current lead to be bonded to an electrode, so that it is not exposed to the inside of an expansion part of the arc tube except for a bonding surface thereof. SOLUTION: Both the tube ends of a translucent ceramic arc tube 1 are formed of a narrow diameter part 2 which is narrower than the diameter of a swelled part provided at a central part of the arc tube 1, and a high-melting point metal current lead 4 made of niobium having a coefficient of thermal expansion close to that of a ceramic with a tungsten electrode 3 welded to one end thereof is inserted along an axis of the narrow diameter part 2 of the translucent ceramic arc tube. The metal current lead 4 and the narrow diameter part 2 are sealed airtightly by an alumina- calcia base sealant 5. Since the metal current lead 4 bonded to the electrode 3 is not exposed to the inside of the ends of the swelled part of the arc tube except for the bonding surface thereof, the deformation of the metal current lead 4 due to the internal pressure at the time of lighting and pressure change at the time of lighting and extinguishing a lamp and generation of leakage due to the deformation can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-high pressure mercury discharge lamp using a translucent ceramic arc tube.

[0002]

2. Description of the Related Art A well-known arc tube structure of a high-pressure discharge lamp using a light-transmitting ceramic arc tube is a metal halide lamp having an end structure as shown in FIG. In the figure, 11 is a translucent ceramic arc tube, 1
2 is a light-transmitting ceramic arc tube thin portion, 13 is an electrode, 14
Is a high melting point metal current introducing body, 15 is a sealing material, and 16 is a plug. This end structure is a low wattage, high color rendering type metal halide lamp and a collection of proceedings of the National Convention of the Illuminating Engineering Society of 1985.
As shown in (P.32), both ends of the arc tube are integrally reduced in diameter, and a niobium metal tube is used as a high melting point metal current introducing body at both ends of the translucent ceramic arc tube. Is used.

By making both ends of the translucent ceramic arc tube smaller in diameter than the central portion (bulging portion), the lamp characteristics are stabilized and the performance is improved. Since the vapor pressure of various additives at the time of lighting is several atmospheric pressures or less, there is no practical problem if the above-mentioned end structure can withstand thermal expansion and thermal shock at the time of lighting.

[0004]

However, in an ultra-high pressure mercury discharge lamp in which the vapor pressure of the additive at the time of lighting becomes 100 atm or more, the internal pressure and pressure change immediately after lighting or when the light is turned off in the conventional end structure. There was a problem that the arc tube was cracked without being able to withstand the heat and leak and rupture of the arc tube occurred, and the reliability was low.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in a conventional discharge lamp using a ceramic arc tube. In the case of a discharge lamp using a ceramic arc tube having a high internal pressure, the discharge lamp is turned on and off. It is an object of the present invention to provide a highly reliable ultra-high pressure mercury discharge lamp that does not cause arc tube leaks or ruptures due to arc tube cracks.

[0006]

In order to solve the above-mentioned problems, the invention according to claim 1 is directed to a light-transmitting ceramic arc tube, a pair of electrodes provided at both ends in the arc tube, and the electrode. A high-melting point metal current introducer joined coaxially is inserted into both ends of the small-diameter portion of the arc tube, and in a super-high-pressure mercury discharge lamp in which mercury and a rare gas are sealed, the high-melting point joined to the electrode is used. Except for the joining surface of the metal current introducing body, the structure is not exposed inside the arc tube bulge end.

According to a second aspect of the present invention, there is provided an ultra-high pressure mercury discharge lamp according to the first aspect, wherein mercury is sealed in the translucent ceramic arc tube so that an internal pressure of the translucent ceramic arc tube becomes 100 atmospheres or more. It is.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention.
FIG. 2 is an enlarged view of a main part. Both tube ends of the translucent ceramic arc tube 1 are the diameter of the bulge at the center of the arc tube (inner diameter 7 mm).
Smaller diameter part 2 (outer diameter 5m
m) is formed, and the length of the small-diameter portion 2 is 20 mm. Along with the axis of the ceramic arc tube small-diameter portion 2, a niobium-made high-melting-point metal current introducer 4 having a coefficient of thermal expansion approximate to that of a φ2 mm ceramic to which a tungsten electrode 3 is welded at one end is inserted. Have been.

The high-melting point metal current introducing member 4 and the small-diameter portion 2 of the ceramic tube are hermetically sealed with an alumina-calcia sealing material 5 having a melting point of about 1400 ° C. Also, a predetermined amount of mercury is sealed in the translucent ceramic arc tube 1 so that the pressure becomes 100 atm during lighting, and argon gas or xenon gas is sealed as a starting gas.

The flash test of the ultra-high pressure mercury discharge lamp having the translucent ceramic arc tube 1 having such a structure and the ultra-high pressure mercury discharge lamp having the arc tube structure shown in FIG. Was. As a result, in the arc tube in which the tip of the high-melting point metal current introducing body 4 as shown in FIG. 3 is exposed inside the arc tube bulging portion, the high melting point metal current introducing body exposed inside the arc tube bulging portion. In some cases, the portion 4 was deformed by the internal pressure, and as a result, many arc tube leaks occurred.

On the other hand, an ultrahigh-pressure mercury discharge lamp having a structure in which the surface other than the bonding surface of the refractory metal current introducing body 4 bonded to the electrode 3 according to the present invention is not exposed to the inside of the arc tube bulge end. No leakage of the arc tube occurred even when the number of blinks was 3,000 or more. That is, by exposing only the joining surface of the refractory metal current introducing body joined to the electrode to the inside of the end portion of the bulging portion of the arc tube, the refractory metal current due to a change in the internal pressure at the time of lighting or a pressure change at the time of lighting or extinguishing. It was found that the deformation of the introduced body and the leakage of the arc tube caused by the deformation were not caused. With this structure, a highly reliable ultra-high pressure mercury discharge lamp free from leakage of the arc tube even when the lamp is blinked 3,000 times or more is obtained.

In the present invention, a niobium tube has been described as a high-melting-point metal current introducing body, but other high-melting-point metals such as molybdenum and stainless steel having similar thermal expansion coefficients may be used. A translucent polycrystalline alumina tube or a translucent alumina-yttrium garnet (YAG) tube having a thermal expansion coefficient similar to that of alumina may be used as the ceramic arc tube.

[0013]

As described above, according to the present invention,
In an ultra-high pressure mercury discharge lamp using a ceramic arc tube, the end of the arc tube has a structure that is integrally reduced in diameter,
It is possible to reduce the internal stress between the ceramic tube and the high-melting-point metal current introducing body due to the internal pressure or blinking at the time of lighting to a level at which there is no practical problem. Then, the occurrence of arc tube cracks due to this is eliminated, stable light emission is obtained until the end of life, and a long-life ultra-high pressure mercury discharge lamp can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention.

FIG. 2 is an enlarged view of a main part showing one embodiment of the present invention.

FIG. 3 is an enlarged view of a main part showing a structure of an arc tube in which a tip portion of a refractory metal current introducing body is exposed inside an arc tube bulging portion.

FIG. 4 is a schematic sectional view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1,11 Translucent ceramic arc tube 2,12 Translucent ceramic arc tube small diameter part 3,13 Electrode 4,14 High melting point metal current introducing body 5,15 Sealing material 16 Plug

Claims (2)

[Claims] 1. A light-transmissive ceramic arc tube, a pair of electrodes provided at both ends in the arc tube, and a high-melting-point metal current guide coaxially joined to the electrodes, the diameter of the arc tube being reduced. In the ultra-high pressure mercury discharge lamp in which mercury and a rare gas are sealed inside, and except for the joining surface of the high melting point metal current introducing body joined to the electrode, the inside of the arc tube bulging end is An ultra-high pressure mercury discharge lamp characterized by a structure that is not exposed. 2. An ultra-high pressure mercury discharge lamp according to claim 1, wherein mercury is sealed in said translucent ceramic arc tube so that the internal pressure becomes 100 atm or more during lighting.