JP3450836B2 - Metal halide lamp - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal halide lamp, and more particularly to a small metal halide lamp for automobile headlights.

[0002]

2. Description of the Related Art In recent years, new small metal halide lamps have been developed and deployed for automobile headlights in place of conventional halogen bulbs. This lamp has the feature that a high luminous flux of about 3 times can be obtained with a low lamp power of 35 W compared with the conventional halogen bulb 55 W, and it is a next-generation vehicle that enables even safer driving of automobiles especially at night. It is being popularized as a high-intensity, energy-saving lamp.

FIG. 4 shows a typical arc tube configuration of such a conventional metal halide lamp for an automobile headlight. In the structure of the arc tube 21 of the lamp, the envelope 22 is made of quartz, and electrodes 23, 24 made of a pair of tungsten rods are provided at both ends of the tube. Each of the rear ends of the tungsten electrodes 23, 24 has an enclosure sealing end 2
Molybdenum foil 27, 28 hermetically sealed to 5, 26
External lead wires 29 made of molybdenum on the other ends of the molybdenum foils 27 and 28, respectively.
30 is welded and joined. In the tube, the luminescent substance 31
Is sodium scandium iodide (NaI
+ ScI ₃ ), ThI ₄ , and metal halides such as LiI,
Mercury and xenon are enclosed as the buffer gas 32. The typical dimension of the arc tube 21 is that the inter-electrode distance Le is 4.
2 mm, arc tube inner diameter φi is 2.7 mm, and tube inner volume is 30 mm ³ at maximum.

Depending on the lamp, as shown in FIG. 5, the tungsten electrode 23 at the end portion 25 of the enclosure is sealed.
A tungsten coil 33 is wound around the periphery of the sealed portion. As disclosed in Japanese Patent Laid-Open No. 10-269941, this is provided in order to prevent quartz cracks / damages at separate locations at the periphery of the electrode sealing portion, and is effective among conventional techniques. Is known to work.

The lighting of the above-mentioned lamp is different from that of a general metal halide lamp for general lighting, and it is operated for repeated flashing including so-called instantaneous restart for automobile headlights more frequently. In order to obtain the luminous flux of the lamp, the lamp current immediately after the lighting is operated at about 2.6 A, which is about 7 times as large as 0.4 A at the time of steady lighting.

One of the main problems in the development of the conventional metal halide lamp of FIG. 4 is that the vicinity of the tips of the molybdenum foils 27 and 28 in the envelope sealing ends 25 and 26 of the arc tube (with the tungsten electrodes 23 and 24). Welding / joining side)
Therefore, the lamp has a short life due to the occurrence of quartz cracks and breakage due to the lighting for a relatively short time. this is,
It can be said that this is a problem related to the unique lighting method as described above.

In order to prevent quartz cracks / damages of the enclosure sealing ends 25, 26 near the peripheral edges of the molybdenum foils 27, 28, in particular, (a) the molybdenum foils 27, 28 have yttrium (Y). ) Or using a high temperature molybdenum material to which indium (In) is added, and (b) reviewing the melting / sealing process conditions by the burner of the molybdenum foils 27, 28 to the envelope sealing ends 25, 26 of the arc tube. To improve,
From these, basically, a means for increasing the adhesion between the molybdenum foils 27 and 28 and the quartz of the enclosure sealing ends 25 and 26 was effective. As a result, the specified life time of 150
It was possible to solve the problem of quartz cracking / damage at 0 hours.

In addition, in Japanese Unexamined Patent Publication No. 8-255594, the sealing length L of the tungsten electrodes 23, 24 at the enclosure sealing ends 25, 26 of FIG. 4 is relatively long, for example 4.0 mm or more. A preventive means of setting the range is disclosed.

The quartz cracks and damages are caused by the luminescent substance 31 of metal halide penetrating into the molybdenum foils 27 and 28 in the vicinity of the peripheral edges thereof.
It has been found that 1 is due to the volume expansion when 1 melts and evaporates by heat conduction from the electrode heated to a high temperature especially at the time of lamp starting. Molybdenum foil 27, 28
It can be said that any means for increasing the adhesiveness between the quartz and the quartz and increasing the sealing length L basically suppresses the intrusion of the light emitting substance 31 into the vicinity of the tips of the molybdenum foils 27 and 28.

The envelope sealing end portion 2 of the above-mentioned arc tube
Quartz cracks / damages that occur near the tips of the molybdenum foils 27 and 28 of Nos. 5 and 26 are (NaI + TlI + InI) and (NaI + Sc) with a life time of 6000 hours or more.
This is a phenomenon observed even at the end of the life of a metal halide lamp for general lighting of (I ₃ ) or (DyI ₃ + TlI) system. Therefore, although this phenomenon occurs for a long time and short time, it can be said that it is a peculiar problem common to all metal halide lamps.

[0011]

Recently, as a new subject for a metal halide lamp for an automobile headlight, there is a long life of the lamp. That is, when various problems including the above-mentioned quartz crack and breakage at the beginning of development are solved, the lamp life time from the initial value of 1500 hours to 2000 hours or more has been requested by the customer. This life time corresponds to an average mileage of about 100,000 km or more of an automobile, which enables the lamp to be handled as a maintenance-free part. This is a great advantage for the customer.

By the way, when actually performing a life test for 1500 hours or more on a conventional metal halide lamp, the above problems (a) and (b) of the prior art are the main problems in the life characteristics of 1500 hours or more. It was also found that in the arc tube used, quartz cracks / damages began to occur again near the edge of the molybdenum foil. Furthermore, the recurrence of such quartz cracks / damages is
It was also found that this is particularly noticeable in the arc tube around which the tungsten coil 33 is wound to prevent quartz cracks and damage at the periphery of the electrode sealing portion as shown in FIG. It is considered that this is because the winding of the tungsten coil facilitates the penetration of the luminescent material into the vicinity of the peripheral edge of the tip of the molybdenum foil.

Further, according to Japanese Unexamined Patent Publication No. 8-255594, means for setting the sealing length L to 4.0 mm or more is 200
It was also found that it cannot be applied to a long-life lamp of 0 hours or more. That is, in such a structure of the arc tube, the amount of the luminescent substance that enters and accumulates in the vicinity of the electrode sealing portion increases with the passage of time, and the luminous flux maintenance factor relatively decreases.

As described above, in the metal halide lamp for automobile headlights, 2000
In order to achieve a long service life of more than an hour, it is a major specific technical task to reliably prevent recurrence of quartz cracks / damages near the tip peripheral edge of the molybdenum foil during the service life of the lamp.

Therefore, in order to solve the above-mentioned conventional problems, the present invention has an enclosure made of quartz, and a molybdenum foil bonded to a pair of electrodes at the end of the tube is hermetically sealed. As a metal halide lamp provided with an arc tube in which a metal halide is sealed as, find an effective means that can prevent quartz cracks and damages that occur near the tip peripheral edge of the molybdenum foil at the envelope sealing end of the arc tube, especially By applying this to a compact metal halide lamp for automobiles, it is possible to reliably prevent recurrence of quartz cracks / damages in the vicinity of the tip edge of the molybdenum foil for 1500 hours or more, and a life time of 2000 to meet customer demand.
It is intended to provide a lamp having a long life of more than hours.

[0016]

In order to achieve the above object, in the metal halide lamp of the present invention, the envelope is made of quartz, and the end of the tube is hermetically sealed with a molybdenum foil bonded to a pair of electrodes. And a light emitting tube in which a metal halide is enclosed as a light emitting substance in the tube, and chromium and molybdenum are provided on the tip end surface of the electrode bonding side of the molybdenum foil sealed at the end of the envelope of the light emitting tube. The solid solution layer is formed.

This prevents quartz cracks and damages that occur in the vicinity of the tip of the molybdenum foil on the electrode bonding side at the sealed end of the envelope of the arc tube, and provides a high quality and long life metal halide lamp. . That is, chrome is quartz
Because of its excellent adhesion with the arc tube sealing end of the arc tube
Of molybdenum foil near the tip of the electrode bonding side
Quartz cracks and damage that occur can be reliably prevented, and higher
You can get a quality and long-life metal halide lamp.

The present invention is particularly preferably applied to a metal halide lamp in which the lamp current immediately after lighting flows three times or more as compared with the lamp current during stable lighting, for example, a small metal halide lamp for automobiles.

As a result, it is possible to prevent the recurrence of quartz cracks / damages in the vicinity of the tip edge of the molybdenum foil when the lighting time is 1500 hours or more, and to obtain a metal halide lamp having a long life of 2000 hours or more in response to the customer's request. To be That is, chromium has excellent adhesion to quartz.
Therefore, if the lighting time is 1500 hours or more,
Recurrence of quartz cracks and damage near the tip edge of the foil
Life is 2000 hours, which is really prevented and meets customer demand
A metal halide lamp is obtained between more longer life
It

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.
3 to FIG. 3 will be described.

FIG. 1 shows a structural diagram of an arc tube of a metal halide lamp 35W for an automobile headlight according to the present invention. This is basically the same as the structure of the arc tube of the conventional metal halide lamp described above. Further, FIG. 2 shows an overall configuration diagram of the metal halide lamp of the present invention.

The structure of the arc tube 1 of the lamp is as follows:
Are made of quartz, and electrodes 3 and 4 made of a pair of tungsten rods at both ends of the tube (electrode rod diameter 0.25 mm, total length 6
The sealing length L is 3.0 mm). Each of the rear ends of the tungsten electrodes 3 and 4 has a yttrium-containing molybdenum foil 7 and 8 (width 1.5 mm, maximum thickness 20 μm) hermetically sealed to the enclosure sealing ends 5 and 6.
m, total length 7 mm), and one end of molybdenum foil 7, 8 is welded and joined to the other end of molybdenum foil 7, 8 (diameter 0.40 mm). In this case, the tungsten coils 11 and 12 (coil wire diameter 0.10 mm, pitch 0.20 m) are attached to the sealed portions of the tungsten electrodes 3 and 4 in the enclosure sealing ends 5 and 6.
The number of turns is 15 and the number of turns is 15). This is for preventing quartz cracking and damage at the periphery of the electrode sealing portion, as described above. In the tube, a light emitting substance 13 of a metal halide
As a main component of, for example, the composition NaI: 70 mass% / ScI
0.2 mg of sodium scandium iodide (NaI + ScI ₃ ) consisting of ₃ : 30% by mass was enclosed, and 0.8 mg of mercury and 0.7 MPa of xenon were used as a buffer gas 14.
Is enclosed. The size of the arc tube 1 is the distance Le between the electrodes.
Is 4.2 mm, the inner diameter φi of the arc tube is 2.7 mm, and the inner volume of the tube is 30 mm ³ at maximum. Moreover, the sealing length L of the tungsten electrodes 3 and 4 at the enclosure sealing ends 5 and 6 is set to 3.0 mm as described above.

As a construction of the completed lamp 15, an outer envelope 16 having the arc tube 1 made of ultraviolet cut glass is used.
It is installed inside, and a cap 17 is attached to the outer envelope 16. Further, the external lead wires 9 and 10 of the arc tube 1 are connected to the terminals of the base 17 through connecting conductor wires 18 and the like.

The lamp 15 is installed in a lamp with a reflecting mirror for an automobile headlight so that the arc tube 1 is in a horizontal position, and a rectangular wave whose frequency during steady lighting is about 100 to 400 Hz is provided by an electronic ballast. It is operated by lighting. Here, as described above, the lamp 15 is lit by the application of a high-voltage pulse voltage of a little less than 20 kV at the time of the instantaneous restart, and immediately after the start, the lamp 15 is lit at a high current about 7 times that of 0.4 A at the steady lighting. Be operated.

The inventor of the present invention has found that the arc tube 1 having the structure shown in FIG.
In the lighting time of 1500 hours or more, it is possible to prevent quartz cracks / damages that occur near the tips of the molybdenum foils 7 and 8 of the enclosure sealing ends 5 and 6 (on the welding side with the tungsten electrodes 3 and 4). I searched for means. As a result, as shown in the enlarged configuration diagram of the container sealing end portion 5 in FIG.
On the tip surface of the metal 19, which reacts with quartz to generate silicate, such as chromium (Cr), aluminum (Al),
Manganese (Mn) or iron (Fe) and molybdenum (M
It has been clarified that the means of forming the solid solution layer 20 with o) is effective in preventing the occurrence of the quartz crack and damage. Then, it was found that chromium (Cr) is most effective among the metals 19. This is the molybdenum foil 7, 8 at the envelope sealing ends 5, 6 of the arc tube 1.
In the sealing step, the metal 19 diffuses and reacts with quartz from the solid solution layer 20 to generate silicate, so that the molybdenum foils 7 and 8 at the sealing end portions 5 and 6 of the metal and the quartz are sealed. This is due to the fact that the adhesiveness of becomes stronger.

The formation of the solid solution layer 20 is basically performed by depositing the metal 19 on the tips of the molybdenum foils 7 and 8 and then diffusing and forming a solid solution by high temperature heat treatment at 1000 ° C. or higher. Here, to attach the metal 19,
There are methods such as vapor deposition, plating and coating.

The inventor used the following method as one method, for example. First, (1) Chromium oxide (CrO ₃ )
/ The tip of molybdenum foil 7, 8 is dipped in an aqueous solution of sulfuric acid (H ₂ SO ₄ ) to adhere CrO ₃ to the surface, and then (2) after drying, in a dry hydrogen (H ₂ ) atmosphere at 1000 to 1100 ° C. By carrying out the reduction treatment with, a solid solution layer 20 of Cr and Mo was formed on the tip portions of the molybdenum foils 7 and 8. Then, the tungsten electrodes 3 and 4 were welded and joined to the respective tip portions of the molybdenum foils 7 and 8.

A lamp 15 was formed from the arc tube 1 using the molybdenum foils 7 and 8 according to the present invention, and the above specified blinking life test was performed for 2000 hours or more. Then, the occurrence of quartz cracks / damages was observed in the vicinity of the peripheral edges of the molybdenum foils 7 and 8 in the envelope sealing ends 5 and 6. As a result, it was confirmed that the quartz cracks and breakage did not occur even after 2500 hours.

The means for forming a solid solution layer with a specific metal on the tip portion of the molybdenum foil according to the present invention has a life time of 60.
(NaI + TlI + InI), (NaI
It was also confirmed that it is effective for preventing the similar quartz crack and damage phenomenon in the metal halide lamp for general lighting of + ScI ₃ ) or (DyI ₃ + TlI) system.

As described above, by providing the structure of the arc tube as shown in the present embodiment, the quartz cracks / damages generated near the tip peripheral edge of the molybdenum foil at the end of the envelope of the arc tube for sealing the envelope are prevented. By applying such a means to a compact metal halide lamp for automobiles, it is possible to reliably prevent recurrence of quartz cracks / damages in the vicinity of the leading edge of the molybdenum foil for a lighting time of 1500 hours or more, and to reduce the life time. A lamp having a long life of 2000 hours or more can be obtained.

[0031]

According to the present invention, the envelope is made of quartz, and the molybdenum foil bonded to the pair of electrodes is hermetically sealed at the end of the tube, and the metal halide is enclosed as the luminescent substance in the tube. It is possible to prevent quartz cracks and damages that occur near the edge of the molybdenum foil electrode bonding side at the sealed end of the envelope of the arc tube, and to stabilize the lamp current immediately after lighting the present invention. By applying to a metal halide lamp that is three times or more the lamp current at the time of lighting, reoccurrence of quartz cracks / damages near the tip peripheral edge of the molybdenum foil at a lighting time of 1500 hours or more is reliably prevented, It is possible to obtain a long-life lamp having a life time of 2000 hours or more in response to customer demand.

[Brief description of drawings]

FIG. 1 is a sectional view of an arc tube of a metal halide lamp for automobiles of the present invention.

FIG. 2 is a cross-sectional view of an essential part of a metal halide lamp for automobiles of the present invention.

FIG. 3 is an enlarged cross-sectional view of the sealed end portion of the envelope of the arc tube of the metal halide lamp for automobiles of the present invention.

FIG. 4 is a sectional view of an arc tube of a conventional metal halide lamp for automobiles.

FIG. 5 is an enlarged cross-sectional view of a sealed end portion of the envelope of the arc tube of the conventional metal halide lamp for automobiles.

[Explanation of symbols]

1 arc tube 2 enclosure 3,4 Tungsten electrode 5, 6 Enclosure sealing end 7,8 molybdenum foil 9, 10 External lead wire 11, 12 Tungsten coil 13 Luminescent substances 14 Buffer gas 15 lamps 16 Outer tube enclosure 17 mouthpiece 18 Connection conductor wire 19 Metals that form a solid solution with Mo 20 Solid solution layer

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 2001-236926 (JP, A) JP 2000-277053 (JP, A) JP 11-238488 (JP, A) JP 10-27574 ( JP, A) JP-A-2-267850 (JP, A) JP-B-37-11397 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01J 61/36

Claims (2)

(57) [Claims] 1. An envelope is made of quartz, and a molybdenum foil bonded to a pair of electrodes is hermetically sealed at a tube end portion,
The tube is provided with an arc tube in which a metal halide is encapsulated as a luminescent material, and the surface of the tip portion of the molybdenum foil, which is sealed at the end portion of the envelope of the molybdenum foil, on the electrode bonding side is fixed with chromium and molybdenum. A metal halide lamp characterized in that a molten layer is formed. 2. The metal halide lamp according to claim 1, wherein the lamp current immediately after lighting is three times or more of the lamp current during stable lighting.