JP2005276471A - Metal halide lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal halide lamp with its extended lifetime. <P>SOLUTION: A translucent airtight container 1 has a discharge space 111 inside an arc tube section 11 and sealing portions 121, 122 formed opposed to each other at the both ends. Inside the sealing portions 121, 122, metal foil 31, 32 composed of an alloy of rhenium and tungsten which is connected to one end of a pair of electrodes 21, 22 arranged opposed to each other in the discharge space 111 is sealed and fitted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a metal halide lamp used for an automobile headlamp or the like.

In a conventional metal halide lamp, a discharge medium containing a halide, a rare gas, or the like is sealed in a discharge space formed inside a light-transmitting hermetic vessel, and ends are sealed at sealing portions formed at both ends of the hermetic vessel. A metal foil made of, for example, molybdenum, which has an electrode joined to the portion, is sealed, and a joint portion between the electrode and the metal foil is covered with a halogen-resistant substance, for example, rhenium metal. (For example, Patent Document 1)
JP-A-6-89703 (3rd and 4th pages, FIGS. 1 and 2)

  In the metal halide lamp of Patent Document 1 described above, even if the halide of the discharge medium enters the sealing portion, the joint portion between the electrode and the metal foil is covered with a halogen-resistant substance. Can be prevented from peeling off.

  However, in order to improve the rise of the luminous flux, a metal halide lamp for automobile headlamps that does not enclose mercury that is charged with twice the rated power at the time of start-up has a high load on the metal foil made of molybdenum. Could not withstand, and fusing occurred. Conversely, if the cross-sectional area of the metal foil is increased in order to withstand high loads, the sealing portion may be affected by the difference in thermal expansion coefficient between the high temperature at the time of forming the sealing portion and the low temperature at room temperature. In some cases, cracks occurred.

  An object of the present invention is to provide a metal halide lamp having a long life by using a metal foil made of an alloy of rhenium and tungsten.

  A light-transmitting hermetic container having a light emitting tube portion forming a discharge space, sealing portions formed at both ends of the light emitting tube portion, one end is disposed opposite to the discharge space, and the other end is sealed. A pair of electrodes sealed in the part and a metal foil made of an alloy of rhenium and tungsten connected to the other end of the electrode and sealed in the sealing part are provided.

  According to the present invention, the life of the lamp can be extended by using a metal foil made of an alloy of rhenium and tungsten.

  Hereinafter, an embodiment of a metal halide lamp of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an overall view for explaining an embodiment of the present invention.

  The hermetic container 1 is made of, for example, translucent quartz glass and has a substantially elliptical arc tube portion 11 and sealing portions 121 formed of the same material as the arc tube portion 11 at both longitudinal ends thereof. 122. The arc tube portion 11 is formed with a substantially cylindrical discharge space 111 in the longitudinal direction thereof. In this discharge space 111, an electrode 21 made of, for example, tungsten extending from the inside of the sealing portions 121 and 122 is formed. , 22 are arranged so that their tips face each other with a predetermined distance between the electrodes.

  In addition, the discharge space 111 is filled with metal halides such as sodium iodide, scandium iodide, zinc iodide, and rare gas xenon as a discharge medium. Metal sodium contained in sodium iodide and metal scandium contained in scandium iodide mainly act as luminescent metals, and the metal zinc contained in zinc iodide is mainly a lamp voltage instead of mercury. Acting as a forming medium, xenon acts primarily as a starting gas. In addition, iodine that forms halides is most suitable as a halide because it is less reactive than others.

  Here, mercury is essentially not contained in the discharge medium sealed in the arc tube portion 11. This “essentially” means that it does not contain any mercury or accepts an amount of mercury of less than 2 mg per cc, preferably 1 mg or less. That is, as in the case of a conventional short arc lamp containing mercury, when the voltage of the discharge lamp is increased to a required level by mercury vapor, 20-40 mg per cc, and in some cases 50 mg or more were enclosed. Compared with this amount of mercury, the amount of mercury less than 2 mg is overwhelmingly small and it can be said that essentially no mercury is contained.

  The sealing portions 121 and 122 are plate-like portions formed by being crushed, and metal foils 31 and 32 are sealed therein. The metal foils 31 and 32 are rhenium-tungsten alloys in which rhenium is mainly composed of tungsten, and have a melting point higher by about 500 ° C. compared to molybdenum that has been conventionally used as a sealing member. It is difficult to react with. Therefore, in the case of a metal halide lamp that does not encapsulate mercury essentially, which requires a high load because high electric power is applied at the time of start-up, the use of rhenium-tungsten as the material of the metal foils 31 and 32 is particularly fusing and sealing. This is effective in suppressing the occurrence of cracks in the parts 121 and 122.

  In the metal foils 31, 32, the introduction conductors 41, 42 are connected to the other end of the electrodes 21, 22 opposite to the connection portion by welding or the like, and the other end of the introduction conductor 42 is a sealing portion It extends outside 122 and is connected to one end of the power supply terminal 5 at a substantially right angle. Since the power supply terminal 5 is formed in an L shape, the other end faces in the direction of the introduction conductor 41 and extends substantially parallel to the sealing portions 121 and 122. An insulating tube 6 is attached to a portion of the power supply terminal 5 parallel to these.

  A cylindrical outer tube 7 made of, for example, a material that blocks ultraviolet rays is provided outside the hermetic container 1 including these so as to cover the longitudinal direction thereof. A diameter-reduced portion 71 is formed at both ends of the outer tube 7. The diameter-reduced portion 71 is glass-welded near the end of the sealing portion 122 in the direction of the anti-light emitting tube portion 11. The other diameter-reduced portion that has not been glass-welded near the end of the sealing portion 121 in the direction of the anti-light emitting tube portion 11.

  The outer tube 7 that covers the airtight container 1 is connected to the socket 9 via a metal tool 8 that is formed so as to sandwich the outer peripheral surface thereof. A metal terminal 91 is formed along the outer peripheral surface of the small diameter portion of the socket 9, and the metal terminal 91 is electrically connected to the inside of the power feeding terminal 5 and the socket 9.

  FIG. 2 is an enlarged view of the vicinity of the arc tube portion for explaining an example of the specification of the metal halide lamp of FIG. The outer diameter R of the arc tube portion 11 is 6.0 mm, the maximum length L in the longitudinal direction is 6.5 mm, and the volume of the discharge space 111 formed by these is 0.02 cc. The size X × Y of the metal foils 31 and 32 made of rhenium-tungsten sealed in the sealing portions 121 and 122 is 1.5 mm × 7.0 mm, and the electrodes 21 and 22 arranged opposite to each other on the axis. The inter-electrode distance D is 4.2 mm. The arc tube portion 11 is filled with 0.8 mg of scandium iodide-sodium iodide-zinc iodide as a metal halide as a discharge medium and 10 atm of xenon as a rare gas, each at room temperature of 25 ° C., Contains no mercury.

FIG. 3 is a diagram showing the number of non-defective products after a flash test of 500, 1000, 1500, 2000, 2500, and 3000 hours in the EU 120 minute mode in the lamp specifications of FIG. 2 equipped with different types of metal foils. Here, Re-W in the figure indicates rhenium-tungsten, and Y ₂ O ₃ -Mo indicates molybdenum that is conventionally used as a material for metal foils.

  Until the test time is 2000 h, the number of defective products generated is small in any metal foil. When the time of 2500h and 3000h elapses, from 3% to 37% by weight, the number of defective products is as small as 2000h, but at 40% by weight, the number of defective products starts to increase from 2500h. Since then, the number of defective products is expected to increase further as time passes. Here, tungsten is not originally a spreadable metal and is not suitable as a sealed conductor as it is, but by synthesizing rhenium, the melting point decreases to a certain weight percent, but the spreadability increases. Since this is up to about 37% by weight, there was little generation of defective products within this range. Further, when the amount of rhenium was further increased and exceeded about 37% by weight, it was confirmed that an intermetallic compound layer was formed. Since this intermetallic compound is generally in a brittle and hard metal state, cracks are likely to occur in the sealing portion. On the other hand, if the weight percentage of rhenium is too low, the spreadability is not sufficient, and cracks are likely to occur in the sealing portion.

  Therefore, the weight% of rhenium in the rhenium-tungsten foil is preferably 37% by weight or less, and more preferably 3% by weight or more and 37% by weight or less.

  In addition, in the molybdenum foil tested for comparison, more defective products are generated. Since melting | fusing point is low compared with rhenium-tungsten, it is thought that fusing generate | occur | produced also on the same test conditions. From this result, it can be seen that rhenium-tungsten is superior to molybdenum as a metal foil material.

  FIG. 4 is a diagram showing the number of non-defective products after turning on the ballast starting power of 90 W and the rated power of 35 W in the lamp specification of FIG. 2 having 26 wt% rhenium-tungsten foil of different thicknesses. is there.

  When the thickness of the rhenium-tungsten foil is 5 μm to 35 μm, the number of defective products hardly occurs, but at 40 μm, the number of defective products suddenly increases. This is because cracks occurred due to the difference in thermal expansion during lamp lighting due to an increase in the contact area between the foil and the sealing portion due to the increase in the thickness of the foil. On the other hand, if the thickness of the foil is less than 5 μm, the cross-sectional area becomes too small, so that the foil cannot withstand high power immediately after starting the lamp, and fusing is likely to occur.

  Accordingly, the thickness of the rhenium-tungsten foil is preferably 5 μm or more and 35 μm or less.

  FIGS. 5 and 6 below show rhenium having a bonding strengthening means that can reduce the occurrence of cracks by improving the bonding between the metal foils 31 and 32 and the sealing portions 121 and 122 and increasing the mechanical strength. -The tungsten foil was tested and its effect was shown.

  FIG. 5 shows the number of non-defective products after holding the lamp temperature at 700, 800, 900, and 1000 ° C. for 1 hour in the lamp specification of FIG. 2 having 26 wt% rhenium-tungsten foil with different surface roughness Ra. FIG. Here, the surface roughness Ra is an average of the roughness with respect to the measurement length, and a rough surface is formed by shot peening that hits a fine grindstone or ice at high speed to process the surface.

  When the surface roughness Ra is 0.05 to 0.50 μm, there are almost no defective products. However, when the surface roughness Ra is 0.65 μm, many defective products appear from the lamp holding temperature of 900 ° C., and at 1000 ° C., the number of defects further increases. Yes. Here, the purpose of roughening the surface is to form minute irregularities on the surface, so that the sealed portion that has become hot is likely to enter the gap during sealing, and it is easy for mutual diffusion to occur. It is to be. Interdiffusion is a mechanism in which different substances move with respect to each other. When the atoms are mixed together, the mechanical strength is improved and cracks are less likely to occur. And it is known that this interdiffusion is more likely to occur in a state where the mutual bites are finer. For this reason, if the surface roughness Ra is too large, the surface unevenness becomes too large, and it is not in a state of being finely bitten, so that mutual diffusion hardly occurs and the mechanical strength is not high. Further, when the surface roughness Ra is 0, since there is no state of biting into each other, mutual diffusion hardly occurs and the mechanical strength is not high.

  Therefore, the surface roughness Ra is preferably 0.05 μm or more and 0.50 μm or less.

  FIG. 6 shows the lamp specification of FIG. 2 having 26 wt% rhenium-tungsten foil with different crystal grain sizes before sealing, after holding the lamp temperature at 700, 800, 900, and 1000 ° C. for 1 hour. It is a figure which shows the number of non-defective products.

  When the size of the rhenium-tungsten foil crystal grains before sealing is 10 μm to 30 μm, no defective product is produced, but at 40 μm, a defective product is produced at 1000 ° C. Here, the rhenium-tungsten foil before sealing has fine crystal grains, and when heated to the sealing portion softening temperature during sealing, these crystal grains recrystallize. For this reason, if the crystal grain before sealing is large, it will grow into a larger crystal grain by heating at the time of sealing, the bonding between the foil and the sealing part will be lowered, and the surface roughness Ra in FIG. 5 is too large. As in the case, the mechanical strength decreases and cracks are likely to occur. In addition, when the crystal grains before sealing are small, the grains can be enlarged by appropriately heating and recrystallizing, so there is no problem even if they are too small.

  Therefore, the size of the crystal grains before sealing with rhenium-tungsten is preferably 30 μm or less.

  FIG. 7 shows a lamp specification of FIG. 2 equipped with 26 wt% rhenium-tungsten foil or a conventional molybdenum foil synthesized with 0.5 wt% yttrium oxide. FIG. 2 is a diagram showing the number of non-defective products after 10,000 cycles with one cycle on for 1.5 minutes and three minutes off, where the melting point of rhenium-tungsten foil is higher than the melting point of molybdenum foil; Was made smaller than the latter.

  With the 26 wt% rhenium-tungsten foil, no defective product was found even after the test, but with the conventional molybdenum foil, many defective products were generated. This is because the conventional molybdenum foil cannot withstand a high power of 90 W at the time of starting, and the foil is blown out. In this regard, it is considered that the rhenium-tungsten foil was able to withstand high power at the start-up because the melting point was high even though the cross-sectional area was about 20% smaller than that of the molybdenum foil.

  Therefore, even if the cross-sectional area of the rhenium-tungsten foil is made smaller than that of the molybdenum foil, it can withstand the same or more power load, so that the fusing of the foil can be reduced and the sealing portions 121 and 122 are swollen. Can be prevented.

  In this embodiment, even if a halide enters the sealing portions 121 and 122, the metal foils 31 and 32 are made of rhenium-tungsten, which is less reactive with halogens. Can be suppressed. In addition, rhenium-tungsten has spreadability, a high melting point, and can withstand high electric power, so that generation of cracks and fusing can be suppressed. Therefore, the lamp life can be extended.

  In addition, embodiment is not necessarily restricted above, For example, you may change as follows.

  The arc tube portion 11 may contain mercury, and even in that case, peeling of the metal foils 31 and 32 and the electrodes 21 and 22, fusing of the foil, and generation of cracks in the sealing portions 121 and 122 can be suppressed, Long life can be realized.

As another bonding strengthening means, the surfaces of the metal foils 31 and 32 may be oxidized and reduced, and the surfaces may be etched. That is, by oxidizing the surface of the foil at around 600 ° C., an oxide film different from rhenium-tungsten is formed, and when the oxide layer is sublimated by reducing it, fine irregularities can be formed on the surface. it can. Thereby, since the sealing parts 121 and 122 and the metal foils 31 and 32 bite into each other, the mechanical strength can be improved and cracks can be hardly generated. Here, the oxygen content at the time of oxidation is preferably 26 atomic% to 65 atomic%. In this range, WO ₃ which is an oxide of tungsten capable of forming fine irregularities on the surface of the foil. This is because the layer is formed stably, so that the bonding is better than the other ranges.

The whole figure for demonstrating one Embodiment of the metal halide lamp of this invention. FIG. 2 is an enlarged view of the vicinity of an arc tube portion for explaining specifications of the metal halide lamp of FIG. 1. The figure which shows the number of good products after a blink test in the lamp | ramp specification of FIG. 2 which comprised the metal foil from which a kind differs. The figure which shows the number of non-defective goods immediately after lighting in the lamp | ramp specification of FIG. 2 which comprised the 26 weight% rhenium-tungsten foil from which thickness differs. The figure which shows the number of non-defective goods after hold | maintaining at each temperature for 1 hour in the lamp | ramp specification of FIG. 2 which comprised the 26 weight% rhenium-tungsten foil from which surface roughness Ra differs. The figure which shows the number of non-defective goods after hold | maintaining at each temperature for 1 hour in the lamp | ramp specification of FIG. 2 which comprised the 26 weight% rhenium-tungsten foil from which the magnitude | size of the crystal grain before sealing differs. The figure which shows the number of non-defective goods after a 10000 cycle lighting / extinguishing test in the lamp | ramp specification of FIG. 2 equipped with 26 weight% rhenium-tungsten foil or the conventional molybdenum foil.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Airtight container 11 Arc tube part 111 Discharge space 21, 22 Electrode 31, 32 Metal foil 41, 42 Introducing conductor 5 Feeding terminal 6 Insulating tube 7 Outer tube 8 Metal tool 9 Base

Claims (1)

A translucent airtight container having an arc tube portion forming a discharge space, sealing portions formed at both ends of the arc tube portion;
One end is disposed oppositely in the discharge space, and the other end is a pair of electrodes sealed in the sealing portion,
A metal halide lamp comprising a metal foil made of an alloy of rhenium and tungsten connected to the other end of each of the electrodes and sealed in the sealing portion.

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