JP2010086742A - Discharge lamp, and discharge lamp device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp capable of suppressing the occurrence of flickering and electromagnetic noise even if a thoria-free electrode is used, and to provide a discharge lamp device. <P>SOLUTION: The discharge lamp includes: an arc tube part 11 having a discharge space 15 formed in its inside; an inner tube 1 having a sealed part 12 formed in a light-emitting part 11; a discharge medium practically containing no mercury, which is filled in the discharge space 15; and an electrode 32 one end of which is sealed to the sealed part 12 and the other end of which is derived to the discharge space 15. The electrode 32 is a thoria free electrode, when its cross-section is set as S(mm2), and a lamp current is set as I(A), 6.5≤I/S≤9.6 is satisfied, and the discharge medium contains a halide of cesium. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a discharge lamp and a discharge lamp device used for an automotive headlamp and the like.

  Discharge lamps used for automobile headlamps, etc. are arcs by providing electrodes in a light emitting part in which a discharge medium such as a rare gas or a metal halide is enclosed in a discharge space and supplying electric power to the electrodes. It has a structure in which discharge is performed. In this type of discharge lamp, it is known that flickering occurs due to movement of the starting point of an arc formed on the electrode surface during lighting. This flickering problem is particularly serious in a discharge lamp that does not substantially contain mercury (hereinafter, a mercury-free lamp). This is because the mercury-free lamp is thinner than the lamp containing mercury and the arc becomes unstable. Conventionally, as this flickering, an electrode containing thorium oxide has been generally used as described in JP-A-2008-16434 (hereinafter referred to as Patent Document 1).

  However, thorium oxide is a radioactive substance, so it is desired to refrain from using it. In view of this, Japanese Patent Application Laid-Open No. 2007-134055 (hereinafter referred to as Patent Document 2) proposes an invention of a mercury-free lamp that can solve problems such as flicker even if it is tria-free.

JP 2008-16434 A JP 2007-134055 A

  The present inventor has also developed a mercury-free lamp using a tria-free electrode capable of suppressing flickering. As a result, in order to suppress the flicker, it is necessary to stabilize the electron emission property, and for that purpose, the current density was found to be a particularly important parameter.

  In the course of this development, a mercury-free lamp using a tria-free electrode also has a problem that electromagnetic noise is likely to occur during startup. This electromagnetic noise causes, for example, flickering of a car navigation monitor or a TV monitor mounted in an automobile, which leads to a problem of reducing their commercial value.

  An object of the present invention is to provide a discharge lamp and a discharge lamp device that can suppress flickering and generation of electromagnetic noise even when a tria-free electrode is used.

  In order to achieve the above object, a discharge lamp according to the present invention includes a light emitting part in which a discharge space is formed, an inner tube having a seal part formed in the light emitting part, and a substance enclosed in the discharge space. In particular, the discharge medium does not contain mercury, one end is sealed to the seal portion, and the other end is an electrode led to the discharge space. The electrode is a tria-free electrode and has a cross-sectional area. When S (mm2) and the lamp current are I (A), 6.5 ≦ I / S ≦ 9.6 is satisfied, and the discharge medium contains a cesium halide.

  According to the present invention, even if a tria-free electrode is used, flicker and generation of electromagnetic noise can be suppressed.

(First embodiment)
The discharge lamp of the present invention will be described below with reference to the drawings. FIG. 1 is a side view for explaining a first embodiment of the discharge lamp of the present invention, and FIG. 2 is a cross-sectional view for explaining the first embodiment of the discharge lamp of the present invention.

  The discharge lamp of FIG. 1 is a discharge lamp used for a headlight of an automobile, and has an inner tube 1 as a main part. The inner tube 1 has an elongated shape, and a substantially elliptical light emitting portion 11 is formed near the center thereof. A plate-like seal portion 12 is formed at both ends of the light emitting portion 11, and a cylindrical portion 14 is continuously formed at both ends via a boundary portion 13. The inner tube 1 is preferably made of a material having heat resistance and translucency, such as quartz glass.

A discharge space 15 having a substantially cylindrical shape at the center and a tapered shape at both ends is formed inside the light emitting portion 11. The volume of the discharge space 15, in the case of vehicle headlights ^are, 10mm ^{3 ~40mm 3,} further is desirably 20mm ³ ~30mm ^3.

  A discharge medium is enclosed in the discharge space 15. The discharge medium is composed of a metal halide 2 and a rare gas.

  The metal halide 2 contains sodium iodide, scandium iodide, zinc iodide, and indium bromide. In addition, cesium iodide is encapsulated in order to prevent electromagnetic noise from being generated at start-up, particularly until the arc is stabilized. The amount of cesium halide enclosed is preferably 0.1% or more and 1.0% or less. The metal halide 2 is not limited to the above combination, but tin halide or the like may be further added. However, it is desirable that the metal halide 2 does not contain thorium halide. Moreover, you may change the kind and combination of the halogen couple | bonded with a metal.

  Xenon is used as the rare gas. The filling pressure of the rare gas can be adjusted depending on the purpose. For example, in order to improve characteristics such as total luminous flux, it is desirable that the sealing pressure is 10 atm or higher, preferably 13 atm or higher at normal temperature (25 ° C.). In addition to xenon, neon, argon, krypton, or the like can be used, or a combination thereof can be used.

  Here, the discharge medium does not substantially contain mercury. This “substantially free of mercury” means that the amount of mercury contained is optimally 0 mg, but it is an amount that is almost equal to that of a mercury-containing discharge lamp that is hardly enclosed. For example, it means that even if a mercury amount of less than 2 mg, preferably 1 mg or less per 1 ml is enclosed, it is allowed.

  The electrode mount 3 is sealed to the seal portion 12. The electrode mount 3 includes a metal foil 31, an electrode 32, a coil 33 and a lead wire 34.

  The metal foil 31 is a thin metal plate made of, for example, molybdenum.

  One end of the electrode 32 is connected to the metal foil 31, and the other end is disposed in the discharge space 15 so as to face each other while maintaining a predetermined distance between the electrodes. The distance between the electrodes is preferably 4.0 mm to 4.4 mm in terms of appearance in the case of an automotive headlamp.

  Here, the electrode 32 is a tria-free electrode. That is, the electrode does not contain thorium or thorium oxide. Examples of such an electrode include a tungsten electrode and a doped tungsten electrode. In addition, in order to suppress generation | occurrence | production of flicker more effectively, it is desirable to contain 30 ppm-100 ppm potassium.

  The electrode 32 is designed to satisfy 6.5 ≦ I / S ≦ 9.6, where S (mm 2) is the cross-sectional area and I (A) is the lamp current. Thereby, flicker can be suppressed over a long period of time. Here, the cross-sectional area is a cross-sectional area of a portion where an arc spot is easily formed, specifically, a cross-sectional area of a portion 0.3 mm from the tip of the electrode. On the other hand, the lamp current is a current value at the time of stable lighting.

  The coil 33 is a metal wire made of, for example, doped tungsten, and is wound spirally around the axis of the shaft portion of the electrode 32 sealed to the seal portion 12. In this coil design, the coil pitch should be 300% or less, the winding length should be 60% or more with respect to the electrode sealing length, and it should not be wound around the shaft portion of the electrode 32 connected to the metal foil 31. .

  The lead wire 34 is a metal wire made of molybdenum, for example. One end thereof is connected to the metal foil 31 on the opposite side to the light emitting portion 11, and the other end is extended to the outside of the inner tube 1 along the tube axis. Among them, one end of an L-shaped support wire 35 made of nickel, for example, is connected to the lead wire 34 on the front end side of the lamp by laser welding. For example, a sleeve 4 made of ceramic is attached to the support wire 35 at a portion parallel to the inner tube 1.

  A cylindrical outer tube 5 is provided concentrically with the inner tube 1 on the outer side of the inner tube 1 configured as described above. These connections are made by welding both ends of the outer tube 5 near the cylindrical portion 14 of the inner tube 1. By this welding, an airtight space is formed between the inner tube 1 and the outer tube 5. This space can be filled with a gas capable of dielectric barrier discharge, such as a kind of gas selected from neon, argon, xenon, and nitrogen, or a mixed gas. The gas pressure is desirably a negative pressure, preferably 0.3 atm or less. The outer tube 5 is preferably made of, for example, a material having an ultraviolet blocking property in which an oxide such as titanium, cerium, or aluminum is added to quartz glass.

  A socket 6 is connected to one end of the inner tube 1 to which the outer tube 5 is connected. These connections are made by attaching a metal band 71 to the outer peripheral surface of the outer tube 5 and sandwiching the metal band 71 with a metal tongue piece 72 formed protruding from the socket 6. Also, a bottom terminal 8a and a side terminal 8b are formed at the bottom of the socket 6, and a lead wire 34 and a support wire 35 are connected thereto, respectively.

One specification of the embodiment of the discharge lamp of the present invention is shown below.
(Example)
Light emitting part 11: made of quartz glass, inner volume of discharge space 15 = 26 mm ³ , maximum inner diameter = 2.5 mm, maximum outer diameter = 6.2 mm, sphere length in the longitudinal direction = 7.8 mm,
Metal halide _{2: ScI 3, NaI, ZnI} 2, InBr, CsI, total = 0.4 mg (of which CsI is 0.4 wt%),
Noble gas: xenon, gas pressure = 13 atm,
Mercury: 0 mg,
Metal foil 31; made of molybdenum,
Electrode 32: made of tungsten containing potassium = 70 ppm, diameter = 0.35 mm, cross-sectional area S = 0.0962 mm ² , distance between electrodes on appearance = 3.74 mm (actual distance between electrodes = 4.32 mm),
Coil 33: Made of doped tungsten, pitch = 200%,
Lead wire 34: made of molybdenum, diameter = 0.6 mm,
Gas in outer tube 5: nitrogen, gas pressure = 0.1 atm.

Start-up power: 75W, (3.0A, 25V),
Stable power: 35W, (0.78A, 45V),
Current density I / S = 8.09 (A / mm ² ).

  In the lamp of this example, it was confirmed that the arc was stable even after the initial period of 2000 hours and further 2000 hours, and flicker did not occur for a long time even in the case of Tria-free. Further, even if a TV monitor was placed near the discharge lamp, the TV monitor did not flicker.

  Next, the current density I / S was changed to confirm the occurrence of flicker during the lifetime. The result is shown in FIG. Here, the current density I / S was adjusted by changing the current value from 0.71 A to 0.92 A and the electrode diameter from 0.30 mm to 0.38 mm. In addition, flicker is ◯ when flicker cannot be recognized when visually observing for 5 minutes after the lamp is in a stable state, Δ when flicker can be recognized when the eyes are closed, and × when flicker cannot be recognized. Judged.

From the results, it can be seen that the initial flicker is likely to occur when the current density I / S is low. This is considered to be because the current density I / S is related to the electron emission, and when the current density I / S is low, the electrode temperature becomes low, the electron emission becomes unstable, and the arc spot easily moves. On the other hand, it can also be seen that when the current density I / S is high, flickering is likely to occur during the lifetime. This is considered to be because when the current density I / S is high, electrode melting constantly occurs during lighting, the shape changes, and the arc spot moves. From the above, even thoria-free electrodes, in order to suppress the flicker in the initial-life, the current density ^{I / S (A / mm 2} ), 6.5 ≦ I / S ≦ 9.6, and more preferably It may be designed to satisfy 7.4 ≦ I / S ≦ 8.7.

  Here, the present inventor has discovered that a new problem that electromagnetic noise is likely to occur at start-up has occurred in the development process of a discharge lamp having such a tria-free electrode. The electromagnetic noise generated at the start-up includes the UHF band (approximately 470 Hz to 770 Hz), which causes the car navigation and TV monitor images mounted on the car to flicker, thus preventing the generation of electromagnetic noise in the UHF band. It is necessary to take measures. Thus, as a result of the inventors' examination of a method for preventing this electromagnetic noise, it was confirmed that a cesium halide is effective.

  FIG. 4 is a diagram for explaining the relationship between the presence / absence of electromagnetic noise and the total luminous flux when the amount of cesium iodide enclosed is changed. The electromagnetic noise was determined to be noise when an abnormal waveform appeared in the UHF band when the waveform was observed using a spectrum analyzer.

  First, in the conventional tria-containing lamp, electromagnetic noise is not generated even if cesium iodide is not enclosed, but in the tria-free lamp that does not contain cesium iodide, electromagnetic noise is generated. The This is presumably because the transition from the arc diffusion mode at the start to the spot mode is performed stably in the tria-containing electrode, whereas it is unstable in the tria-free electrode. Next, in the tria-free electrode lamp in which the amount of cesium iodide encapsulated is changed, the generation of electromagnetic noise is suppressed only by containing a small amount. However, since cesium iodide does not contribute to light emission, it reduces the total luminous flux. Therefore, it can be said that it is desirable to enclose 0.1% or more and 1.0% or less of cesium iodide in the tria-free electrode. Although cesium iodide was used in the test, similar results can be obtained with other halogens.

  In the present invention, it is more effective to adopt the following configuration.

  In order to further suppress the flickering, it is preferable to dope the electrode with potassium. By doping with potassium, the recrystallization of the electrode tip grows long in the tube axis direction, so that minute protrusions are likely to be formed at the electrode tip, and the arc spot is likely to be stabilized at that portion. is there. In order to obtain such an effect and maintain the strength of the electrode, it is desirable that the amount of potassium doped is 30 ppm to 100 ppm.

  In the present invention, the temperature at the tip of the electrode is designed to be relatively high, but the other portions cause cracks in the sealing portion and foil leakage, so the temperature should be low. Therefore, an electrode having a tapered portion 321 at the tip as shown in FIG. 5 or an electrode having a protrusion 322 as shown in FIG. 6 may be used. In addition, the coil is wound around the electrode shaft relatively long (for example, 60% or more with respect to the electrode sealing length), or the distance from the foil end on the discharge space side is 7.0 mm or more away from the electrode tip. It is desirable to adopt.

Therefore, in the present embodiment, when the sectional area is S (mm 2) and the lamp current is I (A), the electrode 32 satisfying 6.5 ≦ I / S ≦ 9.6 is used, and 0 is used as the discharge medium. By enclosing 1% or more and 1.0% or less of cesium iodide, it is possible to suppress the occurrence of flicker over a long period from the beginning of lighting, and to suppress the generation of electromagnetic noise, even with a tria-free electrode. it can. Note that flickering can be further suppressed when the electrode 32 is doped with potassium.
(Second Embodiment)
FIG. 7 is a cross-sectional view for explaining a discharge lamp device according to a second embodiment of the present invention. About each part of this 2nd Embodiment, the same part as each part of the discharge lamp of 1st Embodiment of FIG. 1 is shown with the same code | symbol, and the description is abbreviate | omitted.

  The discharge lamp device according to the present embodiment includes the discharge lamp DL, the reflector 91, the shade 92, the lens 93, the igniter 94, and the ballast 95 according to the first embodiment.

  The reflector 91 is a reflecting mirror having a substantially hyperbolic cross section. A hole is formed in the bottom of the reflector 91, and a shade 92 is provided on the lower side. A discharge lamp DL is inserted into the hole so that the tip of the lamp is covered with the shade 92, and the tube axis is fixed in a substantially horizontal state. Further, a lens 93 for controlling light distribution is provided at the opening of the reflector 91.

  An igniter 94 for applying a high voltage to the lamp and starting it is attached to the socket 6 of the discharge lamp DL. Thereby, the bottom terminal 8a and the side terminal 8b of the discharge lamp DL and the igniter 94 are electrically connected. The igniter 94 is connected to a ballast 95 for lighting the lamp via wiring. The output of the ballast 95 is set to about 35 W when stable, and about 75 W, which is larger than the stable power when starting, for example, twice or more.

  The discharge lamp device composed of these can suppress the occurrence of flicker over a long period from the beginning of lighting, and can also suppress the generation of electromagnetic noise.

The side view for demonstrating 1st Embodiment of the discharge lamp of this invention. Sectional drawing for demonstrating 1st Embodiment of the discharge lamp of this invention. The figure for demonstrating the presence or absence of generation | occurrence | production of the flicker in the initial stage when changing current density I / S, and a lifetime. The figure for demonstrating the relationship between the presence or absence of generation | occurrence | production of electromagnetic noise when changing the enclosure amount of cesium iodide, and a total luminous flux. The 1st modification of an electrode. The 2nd modification of an electrode. The figure for demonstrating 2nd Embodiment of the discharge lamp apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner pipe | tube 11 Light emission part 12 Sealing part 13 Boundary part 14 Cylindrical part 15 Discharge space 2 Metal halide 3 Electrode mount 31 Metal foil 32 Electrode 33 Coil 34 Lead wire 35 Support wire 4 Sleeve 5 Outer tube 6 Socket 71 Metal band 72 Tongue Piece 8a Bottom terminal 8b Side terminal

Claims (4)

A light emitting part in which a discharge space is formed, an inner tube having a seal part formed in the light emission part, a discharge medium substantially free of mercury enclosed in the discharge space, and one end of the seal part The other end comprises an electrode led to the discharge space,
The electrode is a thoria-free electrodes, the sectional area S ^(mm 2), the lamp current when the I (A), together with satisfies 6.5 ≦ I / S ≦ 9.6, the discharge A discharge lamp characterized in that the medium contains a cesium halide.   The discharge lamp according to claim 1, wherein a weight ratio of the cesium halide is 0.1% or more and 1.0% or less.   The discharge lamp according to claim 1 or 2, wherein the electrode is doped with potassium. The discharge lamp according to any one of claims 1 to 3,
A discharge lamp device comprising: a lighting circuit connected to the discharge lamp for supplying larger electric power at the time of starting than at a stable time.

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