JP5493694B2 - Discharge lamp - Google Patents

Description

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

  As is known in Japanese Patent No. 3596812 (hereinafter referred to as Patent Document 1), a discharge lamp used for automobile headlamps has a double tube structure including an inner tube and an outer tube. Yes. The inner tube is composed of a light emitting portion and seal portions formed at both ends thereof. A rare gas or a metal halide is sealed in the light emitting portion, and an electrode mount is sealed in the seal portion.

  This type of discharge lamp requires a voltage of several kV to several tens of kV in order to start the lamp, and it is known that starting is difficult. In view of this, as described in Patent Document 1, an invention has been proposed in which the startability of a lamp is improved by enclosing a gas capable of dielectric barrier discharge in a space formed by an inner tube and an outer tube.

  JP 2003-529194 A (hereinafter referred to as Patent Document 2), JP 2006-80078 (hereinafter referred to as Patent Document 3), JP 2007-42369 A (hereinafter referred to as Patent Document 4), and JP 2008. Japanese Patent No. 527623 (hereinafter referred to as Patent Document 5) proposes an invention that improves the startability of the lamp by forming a conductive film on the outer surface of the light emitting part or the seal part.

Japanese Patent No. 3596812 JP 2003-529194 A JP 2006-80078 A JP 2007-42369 A JP 2008-527623 A

  By adopting the inventions of Patent Documents 1 to 5, the startability of the lamp can be improved. However, when compared with a discharge lamp containing mercury, the current mercury-free lamp still has poor startability, and further improvements are required.

  An object of the present invention is to provide a discharge lamp excellent in startability.

In order to achieve the above object, a discharge lamp according to the present invention is sealed to a light emitting part having a discharge space and an inner tube having a seal part, a discharge medium sealed in the discharge space, and the seal part. In the discharge lamp comprising the electrode mount and the outer tube provided so as to cover the light emitting portion, a gas is sealed in a space formed between the inner tube and the outer tube, A conductive film is formed on the surface of the seal portion so as to be separated from the outer space of the outer tube, and a protuberance or / and an edge portion having a serrated portion on the surface of the seal portion are formed. It is characterized by.

  ADVANTAGE OF THE INVENTION According to this invention, the discharge lamp excellent in startability can be provided.

The side view for demonstrating the discharge lamp of the 1st Embodiment of this invention. The figure for demonstrating the state which rotated the discharge lamp of FIG. 1 90 degrees. The figure for demonstrating the seal | sticker part vicinity of FIG. The figure for demonstrating the formation method of the electroconductive film of this Embodiment. The figure for demonstrating the starting voltage when changing T1 / T2. The figure for demonstrating the discharge lamp of the 2nd Embodiment of this invention. The figure for demonstrating the discharge lamp of the 3rd Embodiment of this invention. The figure for demonstrating the discharge lamp of the 4th Embodiment of this invention.

(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 discharge lamp according to a first embodiment of the present invention, FIG. 2 is a diagram for explaining a state in which the discharge lamp of FIG. 1 is rotated by 90 °, and FIG. FIG. 3 (a) is an enlarged view, and FIG. 3 (b) is a diagram of a cross-sectional view taken along the alternate long and short dash line XX ′ of FIG. 3 (a) from the arrow direction. It is.

  The discharge lamp of FIG. 1 is a so-called D4 type 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. Further, the seal portion 12 is not limited to being formed by a pinch seal, but may be formed by a shrink seal.

Inside the light emitting portion 11, a discharge space 111 having a substantially cylindrical shape at the center and a tapered shape at both ends is formed. The volume of the discharge space 111, in the case of vehicle headlights ^are, 10mm ^{3 ~40mm 3,} further it is appropriate to a 20mm ³ ~30mm ^3. A discharge medium is enclosed in the discharge space 111. The discharge medium is composed of a metal halide 2 and a rare gas.

  The metal halide 2 is composed of a halide such as sodium, scandium, zinc, or indium. Iodine is optimal as the halogen bonded to these metal halides, but bromine, chlorine, and the like may be combined. The combination of metal halides is not limited to this, and tin or cesium halides may be added.

  The rare gas is composed of xenon. The sealing pressure of the rare gas can be adjusted depending on the purpose. For example, in order to improve the characteristics such as the total luminous flux, it is desirable that the sealing pressure is 12 atm or more at normal temperature (25 ° C.). However, the upper limit is about 20 atm at present in production. The pressure of the rare gas is calculated by destroying the boundary between the light emitting unit 11 and the seal unit 12 in water, collecting and measuring the gas in the discharge space 111, and then measuring the volume of the discharge space 111. be able to. In addition to xenon, neon, argon, krypton, or the like can be used as a rare gas, 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 enclosed is optimally 0 mg, but it is almost equal to that of a conventional mercury-containing discharge lamp. This means that an amount of mercury, for example, less than 2 mg per ml, preferably 1 mg or less, is allowed to be contained.

  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. A pattern 311 is formed on the half surface on the electrode 32 side of the surface of the metal foil 31. This pattern 311 is formed by arranging a plurality of non-penetrating semicircular recesses as described in WO2008 / 129745A1, WO2007 / 086527A1, and the like, that is, minute irregularities are formed on the surface. Thereby, while being able to increase the sealing property of sealing glass and foil, generation | occurrence | production of the crack leak which may arise because metal halide 2 and metal foil 31 react can be suppressed. Note that a higher effect can be expected when the pattern 311 is formed on both sides of the foil.

The recesses constituting the pattern 311 can be formed, for example, by irradiating YVO ₄ laser, and the depth, size, etc. thereof can be freely adjusted by the laser output, the method of focusing, and the like. In addition, the array of the recesses can be variously formed by irradiating the laser a plurality of times. For example, by irradiating the laser so as to contact the circumference of the formed recess, the foil as shown in FIG. It is possible to form a pattern in which the recesses are in contact with each other vertically and horizontally on the surface. Further, since the thickness is small, it is possible to control so as not to form dents at the knife edge portions at both ends of the foil which are structurally fragile.

  The electrode 32 is, for example, an electrode made of so-called tritated tungsten obtained by doping tungsten with thorium oxide. One end of the metal foil 31 is overlapped and connected to the light emitting unit 11 side end, and the other end is disposed in the discharge space 111 so as to face each other with a predetermined distance between the electrodes. Yes. 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. The electrode shape is not limited to a straight rod shape, but may be a non-straight rod shape having a large tip diameter or a shape in which the pair of electrodes have different sizes, such as a direct current lighting type. The electrode material may be pure tungsten, doped tungsten, rhenium tungsten, or the like.

  The coil 33 is a metal wire made of, for example, doped tungsten, and is spirally wound around the axis of the shaft portion of the electrode 32 sealed to the seal portion 12. As the coil design, it is preferable that the coil wire diameter is 30 μm to 100 μm and the coil pitch is 600% or less.

  The lead wire 34 is a metal wire made of molybdenum, for example. One end thereof is overlapped and connected to the metal foil 31 on the opposite side with respect to the light emitting unit 11, and the other end extends 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 extending to 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 inner and outer pipes are connected by welding both ends of the outer pipe 5 near the cylindrical portion 14 of the inner pipe 1. Gas is enclosed in a space 51 formed between the inner tube 1 and the outer tube 5. As this gas, a gas capable of dielectric barrier discharge, for example, one kind of gas selected from neon, argon, xenon and nitrogen or a mixed gas can be used. The gas pressure is preferably 0.3 atm or less, more preferably 0.1 atm or less, and even more preferably 0.05 atm or less. The outer tube 5 is preferably made of a material having a thermal expansion coefficient close to that of the inner tube 1 and having an ultraviolet blocking property. For example, quartz glass to which an oxide such as titanium, cerium, or aluminum is added is used. can do.

  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. A bottom terminal 81 is formed at the bottom of the socket 6, and a side terminal 82 is formed at the side. The lead wire 34 and the support wire 35 are connected to the bottom terminal 81 and the side terminal 82, respectively. Yes.

  The discharge lamp constituted by these is connected to a lighting circuit (not shown) so that the bottom terminal 81 is on the high voltage side and the side terminal 82 is on the low voltage side, and the tube shaft is arranged in a substantially horizontal state and is lit. The The output of the lighting circuit is set to, for example, about 35 W when stable, and about 75 W, which is twice or more as much as stable power when starting.

And the conductive film 9 is formed in the part which faces the metal foil 31 among the surfaces of the seal | sticker part 12 of the high voltage | pressure side. Thus, the startability is improved by sealing the gas in the space 51 and forming the conductive coating 9 on the surface of the seal portion 12 set on the high pressure side. This is because when a high voltage for starting the lamp is applied, the glass portion on which the conductive film 9 is formed is polarized, and a dielectric barrier discharge is generated by the gas between the glass portion where the electric charge is accumulated and the outer tube 5. This is because the starting is assisted. In addition, it is effective that the conductive coating 9 has an area of 5 to 20 mm ² . Further, as shown in FIG. 3A, in the state where the conductive film 9 is formed on the pattern 311, the uneven shape of the pattern 311 promotes the polarization immediately after the start, so that the startability is further improved. Can be expected.
The conductive coating 9 is conductive (for example, the resistance of the film is 10 MΩ or less, desirably 50 to 100 kΩ. The resistance value is a tester in which the surface of the film having a thickness of 150 nm is set to 1.5 mm between the terminals. It is desirable to use a material having translucency and heat resistance. For example, indium oxide, tin oxide, zinc oxide, ITO which is an oxide of indium and tin, AZO in which zinc oxide is doped with aluminum oxide, GZO in which zinc oxide is doped with gallium oxide, etc. and fluorine in these A material doped with gallium, antimony, or the like can be used. In the present invention, it is particularly desirable to use inexpensive tin oxide.

  Here, as shown in FIG. 3B, the conductive coating 9 of the present embodiment is composed of a raised portion 91 and a flat portion 92, and the raised portion 91 is conductive so as to surround the flat portion 92. It is formed at the edge of the film 9. The raised portion 91 is a portion that extends in a direction substantially perpendicular to the formation surface and is higher in height than the flat portion 92, and thus has a raised portion that is convex in at least one location of the conductive film 9. Since the electric field is concentrated on the raised portion 91 and the dielectric barrier discharge is easily generated when the starting voltage is applied, the conductive coating 9 is formed in a simple planar shape. Further, the startability can be improved. In particular, when the thickness of the raised portion 91 is T1 (mm) and the thickness of the flat portion 92 is T2 (mm), it is effective that T1 / T2 ≧ 2 is satisfied. The flat portion 92 is allowed even if the film thickness slightly changes, and T2 in that case is an average value.

  Here, a method of forming the conductive film 9 as shown in FIG. 3B will be described with reference to FIG.

  First, as shown in (a), a dispenser 101 is disposed in a non-contact manner in the vicinity of the surface of one seal portion 12 of the inner tube where both ends of the light emitting portion 11 are sealed, and a conductive material obtained by mixing tin oxide and butyl acetate. An acidic solution 9 ′ is dropped on the surface of the seal portion 12. Since the conductive solution 9 ′ has a low surface tension, it tends to spread on the surface as shown in FIG. However, there is a limit to the spread, and when the limit is reached, the conductive solution 9 'accumulates at the end, and the edge rises. Thus, after the raised portion is formed at the edge portion, the conductive film 9 ′ is baked by the hydrogen burner 102 as shown in FIG. 4C, so that the raised portion 91 and the flat portion 92 are formed on the surface of the seal portion 12. The provided conductive film 9 can be formed. In this firing step, it is desirable to heat the conductive film 9 'so that the component of butyl acetate flies and the resistance value becomes about 100 kΩ. The heating means is not limited to a burner. The raised portion 91 of the conductive film 9 thus fired is generally less transparent even with highly permeable tin oxide, ITO, or the like. Therefore, it is possible to visually inspect how much the conductive film 9 is formed. It becomes easy to do.

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 111 = 26 mm ³ , maximum inner diameter = 2.5 mm, maximum outer diameter = 6.2 mm, longitudinal sphere length = 7.8 mm,
Seal portion 12; wall thickness = 2.4 mm, width = 4.1 mm,
Metal halide 2; ScI ₃ , NaI, ZnI ₂ , InBr (= 1: 1.5: 0.4: 0.01), total = 0.4 mg,
Noble gas; xenon, gas pressure = 13 atm,
Mercury; 0 mg,
Metal foil 31; made of molybdenum, length × width = 6.5 mm × 1.5 mm, thickness = 0.02 mm,
Pattern 311; pits having a diameter = 0.02 mm and a depth = 0.003 mm are arranged so as to come into contact with adjacent dents,
Electrode 32: made of triated tungsten, diameter = 0.38 mm, distance between electrodes on appearance = 4.32 mm,
Coil 33; made of doped tungsten, wire diameter = 60 μm, pitch = 250%,
Lead wire 34; made of molybdenum, diameter = 0.4 mm,
Outer tube 5; inner diameter = 7.0 mm, wall thickness = 1.0 mm,
Gas in the space 51; nitrogen, gas pressure = 0.02 atm,
Conductive coating 9: Tin oxide is formed on the high pressure side seal portion 12, area S = 14 mm ² (7 mm ² each on the front and back surfaces of the seal portion 11), film thickness T1 = 0.00035 mm, film thickness T2 = 0 0.0001 mm.

  Whether or not to start using a lighting circuit that continuously outputs a voltage waveform with a starting pulse voltage = 23 kV and a rise time = 250 nsec for a conventional lamp in which a conductive film having a uniform film thickness is formed with the lamp of this embodiment. A test was conducted. As a result, the starting voltage of the example lamp tended to be lower than that of the conventional lamp. In addition, as a result of performing the test with the number increased to 200, the lamp of the conventional example was about 18 kV with poor startability among the tested lamps, whereas the lamp of the example had startability. The bad one was about 16 kV. From this, it can be said that the lamp of the embodiment has less starting variation and less lighting failure.

  Next, a change in the starting voltage when the relationship T1 / T2 between the film thickness T1 of the raised portion 91 and the film thickness T2 of the flat surface 92 was changed was tested. The result is shown in FIG. The number of tests is 200 each.

  As can be seen from FIG. 5, the average value and the worst value (maximum variation) of the starting voltage tend to decrease as T1 / T2 increases. In particular, it is understood that T1 / T2 should be 2 or more. That is, it is desirable to form the conductive film 9 so as to satisfy T1 / T2 ≧ 2. However, when T1 / T2 is in the range of 2 or more, startability does not change so much, and considering the ease of manufacturing, T1 / T2 is preferably 5 or less, and more preferably 3 or less.

  Therefore, in the present embodiment, nitrogen is sealed in the space 51 formed between the inner tube 1 and the outer tube 5, and the raised portion 91 and the flat surface are formed on the edge of the surface of the seal portion 12 set on the high pressure side. Since the conductive film 9 having the portion 92 is formed, an electric field concentrates on the raised portion 91 when a starting voltage is applied, and dielectric barrier discharge is likely to occur. Can be improved. At that time, when the film thickness of the raised portion 91 is T1 (mm) and the film thickness T2 (mm) of the flat surface portion 92, if the conductive coating 9 is formed so as to satisfy T1 / T2 ≧ 2, a high effect is obtained. be able to.

(Second Embodiment)
6A and 6B are diagrams for explaining a discharge lamp according to a second embodiment of the present invention, where FIG. 6A is an enlarged view, and FIG. 6B is a dashed-dotted line XX ′ portion of FIG. It is the figure which looked at the cross section from the arrow direction. 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.

  In the present embodiment, a protrusion 121 is formed on the high-pressure side seal portion 12, and the raised portion 91 is formed by applying the conductive coating 9 to the surface of the seal portion 12 including the protrusion 121. Yes. In this case, the same effect as that of the first embodiment can be obtained. Note that the protrusion 121 may have a height of 0.2 mm or more, and is not limited to one, and a plurality of protrusions 121 may be formed. Further, the protrusion 121 can be used not only for the formation of the raised portion 91 but also as a mark in the lamp manufacturing process.

(Third embodiment)
7A and 7B are diagrams for explaining a discharge lamp according to a third embodiment of the present invention. FIG. 7A is an enlarged view, and FIG. 7B is an enlarged view of a portion indicated by a two-dot chain line Y in FIG. It is.

  In the present embodiment, a serrated portion 93 having a plurality of jagged edges, such as sawtooth teeth, is formed on the edge of the conductive coating 9. Thus, by forming the serrated portion 93 at the edge portion of the conductive coating 9, the electric field is easily concentrated on the tip portion thereof, so that dielectric barrier discharge can be easily generated at the time of starting. Further, the conductive film 93 has the same area, and the longer the edge of the film, the higher the conductive film effect. Therefore, the startability is improved by forming the serrated portion 93 at the edge of the conductive film 9. Can do.

  The conductive film 9 provided with the serrated portion 93 at the edge can be formed, for example, by increasing the dropping height of the conductive solution 9 'in FIG. 4A.

(Fourth embodiment)
FIG. 8 is a diagram for explaining a discharge lamp according to a fourth embodiment of the present invention.

  In the present embodiment, both the raised portion 91 and the sawtooth portion 93 are formed at the edge of the conductive coating 9. That is, the conductive film 9 combines the features of the first and third embodiments, and has a crown-like shape in appearance. With this conductive coating 9, the starting voltage can be lowered by about 4 kV as compared with the case of a flat and smooth coating with the same area.

  The embodiment of the present invention is not limited to the above, and may be modified as follows, for example.

  The conductive coating 9 is not limited to a perfect circle but may be an ellipse or a polygon. Moreover, the shape which combined those shapes or connected mutually may be sufficient.

  Further, the conductive coating 9 is not limited to the surface of the seal portion 12 facing the metal foil 31, and may be, for example, the surface of the seal portion 12 on the electrode 32 or the lead wire 34, or the side surface of the seal portion 12. Good.

  Further, the conductive coating 9 may be formed not only on the surface of the seal portion 12 but also on the inner surface of the outer tube 5. Thereby, startability can further be improved. At this time, it is preferable that the conductive coating formed on the outer tube 5 is formed on the inner surface of the outer tube 5 near the seal portion on the low pressure side so that dielectric barrier discharge is generated in the vicinity of the light emitting portion 11. is there.

  As for the protruding part 91 and the serrated part 93, it is desirable that the tip part is sharper than the arc, and has an acute angle rather than an obtuse angle. Further, the larger the number of formations, the better. By adopting these, the electric field is more easily concentrated on the raised portion 91 and the sawtooth portion 93, so that the startability can be improved.

DESCRIPTION OF SYMBOLS 1 Inner tube 11 Light emission part 111 Discharge space 12 Seal part 2 Metal halide 3 Electrode mount 31 Metal foil 32 Electrode 33 Coil 34 Lead wire 5 Outer tube 51 Space 9 Conductive film 91 Raised part 92 Flat part 93 Serrated part

Claims (4)

An inner tube having a light emitting part having a discharge space inside and a seal part, a discharge medium sealed in the discharge space, an electrode mount sealed in the seal part, and the light emitting part are provided so as to cover In a discharge lamp comprising an outer tube,
Gas is sealed in the space formed between the inner tube and the outer tube, and is disposed on the surface of the seal portion so as to be separated from the outer space of the outer tube, and the surface of the seal portion A discharge lamp comprising a conductive film having a serrated portion on a ridge or / and an edge thereof in contact with the discharge lamp.   The discharge lamp according to claim 1, wherein the raised portion is formed at an edge of the conductive film.   The conductive film has a bulge and a flat surface, and when the film thickness of the bulge is T1 (mm) and the film thickness T2 (mm) of the flat surface, T1 / T2 ≧ 2 is satisfied. The discharge lamp according to claim 1 or 2, characterized in that   A pair of the seal portions are formed at both ends of the light emitting portion, and when the one seal portion side is set to the high pressure side and the other seal portion side is set to the low pressure side, the conductive coating is the high pressure side seal. The discharge lamp according to claim 1, wherein the discharge lamp is formed on a surface of the part.

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