JP2007234266A - Metal halide lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain chromaticity change through restraint of sodium escape during the lifetime. <P>SOLUTION: With the metal halide lamp, a discharge medium not in essence containing mercury with metal halide and rare gas sealed in is included in a discharge space 14 of an airtight vessel 1 equipped with an arc tube part 11 forming the discharge space inside and sealing parts 12a, 12b formed at either end of the arc tube part 11. The sealing parts 12a, 12b have base end parts of a pair of electrodes 2a2, 2b2 sealed, with tip end parts placed in opposition in the discharge space. An outer tube 3 is mounted on the airtight vessel 1 so as to enclose it, and has sodium added by 100 ppm or more. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a metal halide lamp used for automobile headlamps and the like.

  A metal halide lamp that does not enclose mercury is already known, for example, from Japanese Patent Laid-Open No. 11-238488. Such a metal halide lamp that does not enclose mercury can obtain the same or better characteristics without using mercury by combining xenon with halides such as sodium, scandium, zinc, and indium. It has become.

JP 11-238488 A

  However, in such metal halide lamps that do not enclose mercury, the arc floats more thinly than mercury-containing metal halide lamps, so the temperature at the top of the arc tube tends to be higher during lighting, which makes the product lifespan. In addition, sodium can easily escape from the arc tube to the outside of the lamp. When sodium is lost, the ratio to scandium collapses and chromaticity changes occur.

  In response to this problem, Japanese Patent Application Laid-Open No. 2003-109536 describes an invention in which 10 ppm or more of sodium is added to the outer tube. By adopting this configuration, it can be said that the diffusion of sodium from the discharge vessel, that is, the phenomenon of sodium loss can be suppressed.

  Therefore, as a result of the tests conducted by the inventors based on the above-mentioned patent document, the amount of sodium added to the outer tube is regulated to a more suitable amount, so that a change in chromaticity due to sodium loss during the lifetime is remarkably suppressed. I found that I could do it, so I came up with a proposal.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a metal halide lamp capable of suppressing a change in chromaticity by suppressing sodium loss during the lifetime.

  In order to achieve the above object, a metal halide lamp according to the present invention comprises an airtight container having an arc tube portion that forms a discharge space therein, sealing portions formed at both ends of the arc tube portion, and the discharge space. An essentially mercury-free discharge medium encapsulating a metal halide and a rare gas, a proximal end side sealed to the sealing portion, and a distal end side facing a pair of electrodes disposed in the discharge space And an outer tube surrounding the hermetic container, wherein 100 ppm or more of sodium is added to the outer tube.

  According to the present invention, a change in chromaticity can be suppressed by suppressing sodium loss during the lifetime.

(First embodiment)
Hereinafter, a metal halide lamp according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall view for explaining a first embodiment of a metal halide lamp of the present invention.

  The airtight container 1 is made of quartz glass having heat resistance and translucency. The hermetic container 1 has an elongated shape in the lamp axis direction, and a substantially elliptical arc tube portion 11 is formed at a substantially central portion thereof. Plate-shaped sealing portions 12 a and 12 b and cylindrical non-sealing portions 13 a and 13 b are continuously formed at both ends of the arc tube portion 11.

  Inside the arc tube portion 11, a discharge space 14 having a substantially cylindrical shape at the center and a tapered shape at both ends in the axial direction is formed. The volume of the discharge space 14 is 0.1 cc or less for a short arc type discharge lamp, and the volume of the discharge space is 0.01 cc to 0.04 cc when an application is specified for an automobile headlamp. desirable.

  A discharge medium is sealed in the discharge space 14. As the discharge medium, metal halide and rare gas are used.

  Metal halides include sodium, scandium halide, which mainly acts as a luminescent medium that generates visible light, zinc halide, which acts as a lamp voltage forming medium, and indium luminescence for the purpose of improving emission chromaticity during lighting. Of halide is enclosed. Most preferably, halides bound to these metals are bound to iodine, which is less reactive among halides. However, the halide to be bonded is not limited to iodine, but may be bromine or chlorine, or a plurality of halides may be used in combination.

  As the rare gas, xenon which has high luminous efficiency immediately after starting and mainly acts as a starting gas is enclosed. In addition to xenon, neon, argon, krypton, or the like may be used, or a combination thereof may be used. At that time, the filling pressure of the rare gas is preferably 9 to 15 atm.

  Here, the discharge medium is essentially free of mercury. This “essentially mercury-free” includes a mercury amount range of 2 mg or less, preferably 1 mg or less, more preferably 0 mg per cc. Considering that the amount of mercury was 20 to 40 mg per cc, which was enclosed in a conventional short arc type mercury-containing metal halide lamp, and in some cases 50 mg or more, this amount of mercury was essentially free of mercury. It can be said.

Mounts 2a and 2b are sealed inside the sealing portions 12a and 12b.
The mounts 2a and 2b include metal foils 2a1 and 2b1, electrodes 2a2 and 2b2, coils 2a3 and 2b3, and external lead wires 2a4 and 2b4.

  Metal foils 2a1 and 2b1, for example, thin metal plates made of molybdenum.

  The electrodes 2a2 and 2b2 are made of, for example, a material obtained by mixing thorium oxide with tungsten, and are connected to end portions on the arc tube portion 11 side of the metal foils 2a1 and 2b1 by welding. The shape is a stepped shape in which the distal end side is formed to have a larger diameter than the proximal end side, and the distal end side of the large diameter maintains the predetermined inter-electrode distance in the discharge space 14, and the distal ends of each other Are arranged so as to face each other, and the proximal end side of the small diameter is sealed inside the sealing portions 12a and 12b. Here, the “predetermined interelectrode distance” is preferably 5 mm or less for a short arc lamp, and further about 4.2 mm when used for an automobile headlamp.

  The coils 2a3 and 2b3 are made of, for example, doped tungsten, and are spirally wound around the peripheral surfaces of the electrodes 2a2 and 2b2. The region in which the coils 2a3 and 2b3 are wound is approximately 3.0 mm from the ends of the metal foils 2a1 and 2b1 in the direction of the arc tube 11.

  The external lead wires 2a4 and 2b4 are made of, for example, molybdenum, and are connected to end portions of the metal foils 2a1 and 2b1 on the opposite side to the arc tube portion 11 by welding or the like. The other end sides of the external lead wires 2a4 and 2b4 extend outside the sealing portions 12a and 12b along the tube axis.

  A cylindrical outer tube 3 having an action of blocking ultraviolet rays by adding an oxide such as titanium, cerium, or aluminum to quartz glass is provided outside the hermetic container 1 configured as described above. Along the airtight container 1, the airtight container 1 is provided concentrically. These connections are made by melting the cylindrical non-sealing portions 13a and 13b at both ends of the hermetic container 1 and both ends of the outer tube 3. Further, 100 ppm or more of sodium is added to the outer tube 3. Here, sodium may be applied not only to the outer tube 3 but also to the inner surface of the outer tube 3 in the form of sodium hydroxide or the like. At that time, sodium includes not only the case where it is added in an elemental state but also the case where it is added in an oxidized state. Note that sodium added to the outer tube 3 can be measured by using, for example, plasma spectroscopy.

  The space formed by the airtight container 1 and the outer tube 3 is kept completely airtight. Note that, for example, nitrogen can be sealed in the space, or a rare gas such as neon, argon, xenon, or the like can be sealed or mixed.

  A socket 4 is connected to the sealing portion 12a side of the outer tube 3 with the airtight container 1 covered inside. For this connection, a metal band 51 mounted on the outer peripheral surface of the outer tube 3 in the vicinity of the non-sealing portion 13a is connected to four metal tongue pieces formed on the opening end of the socket 3 on the airtight container 1 holding side. 52 (two are shown in FIG. 1). And in order to strengthen those connections further, the contact point of the metal band 51 and the tongue piece 52 is welded by the laser.

  A strip-like terminal 41 for supplying power from the lighting circuit is formed along the outer peripheral surface of the end portion of the socket 4 on the side opposite to the light emitting tube portion 11. The strip terminal 41 is connected to the external lead wire 42 via the support wire 61. A portion of the support wire 61 that is substantially parallel to the tube axis is covered with an insulating tube 62 made of ceramic.

  These metal halide lamps are arranged with the tube axis in a substantially horizontal state, and are lit at about 35 W when stable, and at about 75 W, which is twice or more as much as stable power when starting.

  FIG. 2 is an enlarged view for explaining one specification of the metal halide lamp of FIG. The following tests are performed based on this specification unless otherwise specified.

Discharge vessel 1: made of quartz glass, volume of discharge space 14 = 0.02 cc, inner diameter A = 2.5 mm, outer diameter B = 6.2 mm, longitudinal sphere length C = 7.8 mm,
Distance D = 0.4 mm between arc tube portion 11 and outer tube 3
Metal halide = ScI3: NaI: ZnI2: InBr, total encapsulated amount = 0.60 mg
Noble gas: xenon = 10 atm,
Mercury: 0 mg,
Metal foils 2a1, 2b1: made of molybdenum,
Electrodes 2a2, 2b2: made of triated tungsten, tip diameter = 0.40mm, base end diameter = 0.30mm, distance between electrodes E = 4.2mm,
External lead wires 2a4, 2b4: made of molybdenum, diameter = 0.6 mm,
Outer tube 3: Titanium oxide = 400 ppm, Cerium oxide = 4500 ppm, Space between sodium-tight container 1 and outer tube: Nitrogen, Pressure = 0.1 atm
FIG. 3 is a diagram showing a change in chromaticity x depending on the amount of sodium added. The lighting condition is a flash cycle of the EU 120 minute mode defined in JEL215, which is a standard for an automobile headlamp HID light source.

  From the results, it can be seen that changing the amount of sodium added to the outer tube 3 affects the amount of change in chromaticity x during the lifetime. That is, as the amount of sodium added to the outer tube 3 is larger, the tendency of change in the chromaticity x is less overall. A similar tendency can be obtained for the chromaticity y.

  Here, what should be particularly noted is the maximum chromaticity change amount. That is, in all lamps in which the amount of sodium added to the outer tube 3 is changed, the chromaticity x tends to change most between 500 hours and 1000 hours, but attention is paid to the maximum chromaticity change amount at this time. To do.

  FIG. 4 shows the maximum change in chromaticity x up to 2000 hours. From the results, the maximum chromaticity change decreases as the amount of sodium added to the outer tube 3 increases. And when it exceeds 100 ppm, it can confirm that the tendency is remarkable.

  Thus, when sodium is added to the outer tube 3, the sodium is disposed in the space between the airtight container 1 and the outer tube 3 during lighting, and the sodium concentration in the space increases, so that the inside of the arc tube unit 11 is increased. It is known that sodium loss is suppressed. However, when the sodium concentration is 100 ppm or more, the chromaticity change indicating sodium omission is greatly improved because the diffusion of sodium in the arc tube portion 11 is suppressed and the airtight container 1 and the outer tube 3 are not. It is expected that sodium in the space between them has entered the arc tube portion 11. That is, even when the sodium concentration in the space between the hermetic container 1 and the outer tube 3 is increased to some extent, even if a phenomenon occurs in which excess sodium penetrates the wall of the arc tube portion 11 and enters the inside. It is not strange. However, it is difficult to confirm whether or not the sodium added to the outer tube 3 has entered the arc tube portion 11 during the lifetime because sodium is sealed in the arc tube portion 11 from the beginning.

  Therefore, the amount of sodium added to the outer tube 3 is desirably 100 ppm or more from the results of FIG. There is no particular upper limit for the amount of sodium added, but if the amount added is too large, the outer tube may become cloudy and the luminous efficiency may decrease, so it is preferably 3000 ppm or less.

  Therefore, in the present embodiment, in a metal halide lamp that does not enclose mercury, chromaticity change during the lifetime can be remarkably suppressed by adding 100 ppm or more of sodium to the outer tube 3.

The whole figure for demonstrating 1st Embodiment of the metal halide lamp of this invention. The enlarged view for demonstrating one specification of the metal halide lamp of FIG. The figure which shows the change of the chromaticity x by the addition amount of sodium. The figure which shows the largest change of the chromaticity x to 2000 hours when changing the quantity of the sodium added to the outer tube | pipe.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Airtight container 11 Arc tube part 12a, 12b Sealing part 13a, 13b Non-sealing part 14 Discharge space 15 Metal halide 2a, 2b Mount 2a1, 2b1 Metal foil 2a2, 2b2 Electrode 2a3, 2b3 Coil 2a4, 2b4 External lead wire 3 Outer tube 4 Socket 51 Metal band 52 Tongue piece 61 Support wire 62 Insulating tube

Claims (1)

An airtight container having an arc tube portion that forms a discharge space therein, and sealing portions formed at both ends of the arc tube portion;
An essentially mercury-free discharge medium in which a metal halide and a rare gas are enclosed in the discharge space;
The proximal end side is sealed to the sealing portion, and the distal end side is a pair of electrodes arranged opposite to each other in the discharge space,
An outer tube surrounding the airtight container,
A metal halide lamp, wherein 100 ppm or more of sodium is added to the outer tube.

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