JP2008181681A - Metal halide lamp, lighting device, and vehicular headlight device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the lifetime characteristics of a mercury-free metal halide lamp. <P>SOLUTION: The metal halide lamp includes a discharge vessel 1, having a discharge space 14 and sealing sections 12a, 12b. The discharge vessel 1 contains a halogenated metal and rare gases, and a discharge medium is enclosed, in the vessel essentially without containing any mercury. A pair of electrodes 3a2, 3b2 is arranged opposingly in a discharge vessel 11, and ends at the side of the base part of the electrodes are joined to pieces of metal foil 3a1, 3b1, respectively. An external lead 5 is joined to the other end sides of the pieces of metal foil 3a1, 3b1. In this state, the pieces of metal foil 3a1, 3b1 are sealed airtightly by the sealing sections 12a, 12b. A region including the junction section of the pieces of metal foil 3a1, 3b1 and the electrodes 3a2, 3b2 is coated with coating films 4a, 4b formed by at least one type of fine particle 31 selected from metal and a metal oxide, thus suppressing the reaction with the discharge medium and prolonging the lifetime of the lamp. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a metal halide lamp, a lighting device for the lamp, and an automotive headlamp device.

Conventional mercury-free metal halide lamps that do not use mercury have a problem in that the metal foil made of molybdenum foil or the like that ensures the airtightness of the discharge vessel is likely to react with the discharge medium. In order to prevent the reaction with the discharge medium and to improve the life characteristics due to the absence of mercury. (For example, Patent Document 1)
JP 2002-260581 A

  In the technique of Patent Document 1 described above, even when the coating film is formed on the entire metal foil, a crack occurs in the coating film due to the difference in thermal expansion coefficient between the coating film and the metal foil during sealing. Since the discharge medium permeates through the crack, there is a problem that a crack or the like is generated in the sealing portion, causing a factor that adversely affects the long life.

  SUMMARY OF THE INVENTION An object of the present invention is a metal halide lamp that essentially does not use mercury, a metal halide lamp that has been improved such as a decrease in life characteristics caused by not using mercury, a metal halide lamp lighting device using the lamp, and an automobile An object of the present invention is to provide a headlight device for use.

  In order to solve the above-described problems, a metal halide lamp of the present invention includes a discharge vessel having a discharge space and sealing portions provided at both ends of the discharge space, and a metal halide sealed in the discharge vessel. A discharge medium containing noble gas and essentially free of mercury; a pair of electrodes disposed opposite to each other in the discharge space; and a base side end of each of the pair of electrodes; and A metal foil hermetically sealed by a sealing portion; a pair of external leads respectively joined to the other end side of the metal foil and led out of the discharge vessel; and the electrode of the metal foil And a coating film formed of fine particles made of at least one selected from metals and metal oxides.

  According to the above-described means, the reaction between the metal foil and the free halogen or metal halide in the discharge medium can be suppressed by the coating film. It is possible to extend the life by suppressing the occurrence of leakage and further rupture.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  1 to 3 are diagrams for explaining a first embodiment of the metal halide lamp according to the present invention, FIG. 1 is a schematic configuration diagram, and FIG. 2 is a front view showing an enlarged main part of FIG. FIG. 3 is an enlarged cross-sectional view showing a main part of FIG.

  Reference numeral 1 denotes an inner tube constituting a metal halide lamp. Plate-shaped sealing portions 12a and 12b are formed at both ends of the discharge vessel 11 at the center, and cylindrical unsealed at both ends. Stop portions 13a and 13b are formed. The inner tube 1 can be used as long as it is a material excellent in heat resistance and translucency. For example, quartz glass can be used.

  Inside the discharge vessel 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 preferably 100 μl or less for a short arc type discharge lamp, and the volume of the discharge space is preferably 10 μl to 40 μl when an application is specified for an automotive headlamp.

  The discharge space 14 is filled with a discharge medium composed of the metal halide 2 and a rare gas, and the discharge medium essentially does not contain mercury. Next, a specific example of the discharge medium will be described.

  First, as the metal halide, halides of various metal elements can be used. For example, a first metal halide that mainly contributes to light emission is used. As the first halide, a halide of one or more kinds of metal elements selected from sodium (Na), scandium (Sc), and a rare earth metal is used. Na and Sc are particularly efficient luminous materials.

  The metal halide has a vapor pressure that is relatively high and includes one or more types of metal halides that do not easily emit light in the visible light region as compared to the metal of the first halide as the second halide. Can do. The metal that does not easily emit light in the visible light region has a higher energy level than the metal of the first halide and may be in a state where the metal of the first halide mainly emits light. By adding the second halide, a lamp voltage close to that of a lamp containing mercury can be obtained, and the electric and light emission characteristics of the mercury-free metal halide lamp can be improved. The second halide contributes to chromaticity improvement and the like.

  Examples of the second halide include magnesium (Mg), iron (Fe), cobalt (Co), chromium (Cr), zinc (Zn), nickel (Ni), manganese (Mn), aluminum (Al), and antimony. One or more metal halides selected from (Sb), beryllium (Be), rhenium (Re), gallium (Ga), indium (In), titanium (Ti), zirconium (Zr) and hafnium (Hf) Is used.

  Further, the metal halide may contain a third halide. In the third halide, for example, tin (Sn) is added as a component that contributes to the suppression of free halogen, and cesium (Cs) is added as a component that corrects the distribution of the arc temperature to reduce heat loss.

  As the halogen constituting the metal halide, iodine (I) is most suitable in terms of low reactivity, and the reactivity increases in the order of bromine (Br), chlorine (Cl), and fluorine (F), but is necessary. It is possible to select appropriately according to. Further, different halogen compounds such as iodide and bromide can be used in combination.

  As for the amount of metal halide to be enclosed, for example, the first halide that mainly contributes to light emission can be enclosed in the range of 5 mg to 110 mg per 1 cc of the internal volume of the discharge vessel (volume of the discharge space). A more preferable range is 5 mg to 35 mg per 1 cc of the internal volume of the discharge vessel. In such a range, the rise of the luminous flux can be accelerated and the light color can be stabilized. The second halide can be enclosed in the range of 0.05 mg to 200 mg per 1 cc of the internal volume of the discharge vessel. About other halides, it adjusts suitably.

  In addition to the starting gas and the buffer gas, the rare gas acts to emit main light immediately after the starting. Generally, there is no particular limitation as long as it does not pass through the hermetic container, but argon (Ar), krypton (Kr), or xenon (Xe) is recommended when the hermetic container is formed of quartz glass. When light emission immediately after start-up depends on a rare gas, xenon is optimal because xenon has the highest luminous efficiency.

  When the enclosure pressure of the rare gas is increased, the lamp voltage is increased, and the lamp input can be increased for the same lamp current to improve the rising characteristics of the luminous flux. Good rise characteristics of the luminous flux are convenient for any purpose of use, but are particularly important for automotive headlamp devices and liquid crystal projectors. For example, the rare gas is sealed at a pressure of 3 atm or more, and is preferably sealed in a range of 5 to 15 atm.

  Further, “essentially no mercury is enclosed” is not limited to the state where mercury is not enclosed at all, and it is acceptable that less than 2 mg of mercury, preferably 1 mg or less of mercury exists per 1 cc of internal volume of the discharge vessel. Means. However, it is environmentally desirable that mercury is not encapsulated. In the case where the electrical characteristics of the discharge lamp are maintained by the conventional mercury vapor, the short arc type is filled with 20 mg to 40 mg of mercury per 1 cc of the internal volume of the discharge vessel, and in some cases, 50 mg or more of mercury. The amount of mercury used in is essentially low.

  In FIG. 1 again, mounts 3a and 3b are sealed inside the sealing portions 12a and 12b. The mounts 3a and 3b include metal foils 3a1 and 3b1, electrodes 3a2 and 3b2, and lead wires 3a3 and 3b3.

  The metal foils 3a1 and 3b1 are strip-shaped thin metal plates having a high melting point such as molybdenum. As shown in FIGS. 1 and 2, coating films 4a and 4b are applied to the electrodes 3a2 and 3b2 side of the metal foils 3a1 and 3b1, respectively. The coating films 4a and 4b are formed of fine particles 31 made of at least one material selected from the metals and metal oxides shown in FIG. Since the coating films 4a and 4b are sealed together with the metal foils 3a1 and 3b1 by the sealing portions 12a and 12b, the constituent material is a high melting point material that does not change with respect to heating conditions at 1500 ° C. for 5 seconds to 60 seconds. preferable.

  Here, the fine particles 31 forming the coating films 4a and 4b are fine particles in order to make it difficult for the free halogen gas and the metal halide gas to diffuse in the coating film. The coating films 4a and 4b can be formed of, for example, metal oxide fine particles having a thickness of about 20 nm to 100 nm as tried this time, thereby obtaining a good halogen resistance effect.

  Examples of the metal material for the coating films 4a and 4b include platinum (Pt), tantalum (Ta), tungsten (W), molybdenum (Mo), rhenium (Re), niobium (Nb), vanadium (V), zirconium (Zr). ), Hafnium (Hf), holmium (Ho), dysprosium (Dy), yttrium (Y), scandium (Sc), and boron (B). The metal material is not limited to being used as a single metal, but may be used as an alloy containing the above metal element.

As the metal oxide, silica (SiO ₂ ), alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), hafnia (HfO ₂ ), yttria (Y ₂ O ₃ ), holmium oxide (Ho ₂ O ₃ ). , Dysprosium oxide (Dy ₂ O ₃ ), scandium oxide (Sc ₂ O ₃ ), and tantalum oxide (Ta ₂ O ₅ ). These compounds may be used as a mixture of plural kinds, or may be a complex oxide such as YAG.

  Since the coating films 4a and 4b made of the above-described materials can suppress the reaction with halogen or metal halide, the occurrence of cracks in the sealing portions 12a and 12b due to this reaction, and further the occurrence of rupture, etc. It becomes possible to suppress significantly. Therefore, the lifetime of the mercury-free metal halide lamp can be extended more reliably.

  The coating films 4a and 4b first suppress the reaction between the metal foils 3a1 and 3b1 and, in particular, free halogen or metal halide in the discharge medium, and these gases diffuse in the coating film to cause the metal foil 3a1. , 3b1 can be suppressed by the fine particles 31.

  The coating films 4a and 4b are formed so as to cover regions including the joint portions of the metal foils 3a1 and 3b1 with the electrodes 3a2 and 3b2. That is, the portion where the free halogen gas or metal halide gas in the discharge medium enters is the end of the joint between the metal foils 3a1 and 3b1 and the electrodes 3a2 and 3b2, and the coating film is coated so that at least such portions are covered. Form. The coating films 4a and 4b may be formed only on one side region of the metal foils 3a1 and 3b1 including the joints with the electrodes 3a2 and 3b2, but both sides of the end portions on the discharge space 14 side of the metal foils 3a1 and 3b1 Further, it may be formed so as to cover the entire surface of the metal foil including the edge portion and the end surface on the discharge space 14 side.

  The method for forming the coating film is not limited to the above, and a region including the joint portions of the metal foils 3a1 and 3b1 with the electrodes 3a2 and 3b2 by applying a solution baking method, an electrostatic coating method, or the like. A coating film may be formed.

  When applying the coating and firing method of the solution, first, a metal oxide fine particle is dispersed in an organic solvent, water, or the like to prepare a slurry solution, which is applied to necessary portions of the metal foils 3a1 and 3b2 and dried. Thereafter, the coating films 4a and 4b can be formed by firing under conditions in which the metal foils (for example, Mo foils) 3a1 and 3b1 are not significantly oxidized or deteriorated.

  The coating films 4a and 4b may be formed on the metal foils 3a1 and 3b1 before the electrodes 3a2 and 3b2 are bonded, or may be formed after the electrodes 3a2 and 3b2 are bonded to the metal. When the coating film is formed after the electrode is bonded to the metal foil, the coating film covers not only the surface of the metal foil but also the base side surface of the electrodes 3a2 and 3b2 in the vicinity of the bonding portion of the electrode with the metal foil. Can be formed. The film thickness of the coating films 4a and 4b is 50 nm or more and 10% or less of the maximum thickness of the metal foils 3a1 and 3b1.

  In this embodiment, the metal foil is coated with a coating film of fine particles made of at least one selected from metals and metal oxides at least in a predetermined region from the electrode side. As a result, when the discharge medium penetrates into the sealing portion due to the electrode not being completely in close contact with the sealing portion of the discharge vessel, the portion of the coating film where the discharge medium cracks or the coating By making the distance to reach the metal foil that is not coated with the fine particles constituting the coating film, the reaction with the free halogen or metal halide in the discharge medium can be suppressed.

  Therefore, since the problems peculiar to mercury-free metal halide lamps can be improved with a coating film made of fine particles, it is possible to suppress the deterioration of the life characteristics due to non-lighting due to metal foil breakage, crack leakage, and the occurrence of rupture. Longer service life can be realized.

  4 and 5 are diagrams for explaining a second embodiment of the metal halide lamp according to the present invention. FIG. 4 is an enlarged view of a main part corresponding to FIG. 2, and FIG. 5 is a cross-sectional view corresponding to FIG. , The electrode side of the lamp is shown, and the other electrode side is the same, and the illustration is omitted.

  In this embodiment, as shown in FIG. 4, in the vicinity of the joint between the metal foil 3a1 and the electrode 3a2, as shown in FIG. 5, at least one kind of fine particles 31 and needle-like particles 51 selected from metal and metal oxide are used. Is coated with the coating film 4a formed in (1). The coating film 4a is formed so as to cover a region including a joint portion between the metal foil 3a1 and the electrode 3a2. The coating film 4a has a film thickness of 50 nm or more and 10% or less of the maximum thickness of the metal foil 3a1, as in the first embodiment.

  Here, the acicular particles 51 have a shape in which the width of the cross-section perpendicular to the axis in the longitudinal direction of the particles is about 20 nm to 100 nm, which is the same as that of the fine particles, and extends long along the axis in the longitudinal direction of the particles. is doing.

  The coating film of this embodiment prevents the peeling from the metal foil by including needle-like particles, and is more effective in suppressing the reaction between the metal foil and the discharge medium, particularly free halogen and metal halide. .

  FIG. 6 is a cross-sectional view corresponding to FIG. 3 for describing a third embodiment relating to the metal halide lamp of the present invention.

  In this embodiment, the coating film 4a is formed only on the bonding surface side between the metal foil 3a1 and the electrode 3a2, and the film formation range t (see FIG. 4) of the coating film 4a is, for example, 3 mm from the electrode 3a2 side. And

  That is, if the coating film 4a is formed on the bonding surface side between the metal foil 3a1 and the electrode 3a2, free halogen and metal halide that have entered the sealing portion 12a through the electrode 3a2 are diffused by the coating film 4a. It is suppressed. When cracks occur in the same part of the coating film, the fine particles 31 of the coating film 4a can increase the distance until the metal foil 3a1 reacts particularly with free halogen or metal halide in the discharge medium, thereby suppressing the reaction. It becomes.

  Next, examples of mercury-free metal halide lamps and evaluation results thereof will be described with reference to FIGS.

  FIG. 7 illustrates a conventional example of the coating layer formed on the metal foils 3a1 and 3b1 and Examples 1 to 4, and FIG. 7 illustrates a lamp life based on different coating layers.

As for the discharge vessel 11, an airtight vessel made of quartz glass having an outer diameter a of 6.5 mm and an inner diameter b of 3 mm as shown in FIG. 1 was used. The electrodes 3a2 and 3b2 were made of tungsten having an outer diameter c of 0.4 mm, and the distance d between the electrodes 3a2 and 3b2 was 4.2 mm. Among the discharge media, for the metal halide, ScI ₃ , NaI and ZnI ₂ are used, and these ratios are set to ScI ₃ : NaI: ZnI ₂ = 3: 5: 2 by volume ratio, and 1 mg is enclosed in the total amount. did. Xe was used as the rare gas, and Xe was sealed at 10 atm.

  Further, metal foils 3a1 and 3b1 having a thickness of 20 μm and a length of 10 mm are prepared. After electrodes 3a2 and 3b2 are welded, metal foils 3a1 and 3b1 and electrodes 3a2 and 3b2 are coated in the following embodiments, respectively. Films 4a and 4b are formed.

In Example 1, the coating films 4a and 4b of Al ₂ O ₃ fine particles 31 having an average particle diameter of 20 nm were formed with a film thickness of 0.3 μm by an aqueous solution coating and baking method.

In Example 2, the coating films 4a and 4b of Sc ₂ O ₃ fine particles 31 having an average particle diameter of 120 nm were formed with a film thickness of 0.5 μm by an aqueous solution coating and baking method.

In Example 3, a mixed film of the needle-like particles 51 of the coating films 4a and 4b and the Al ₂ O ₃ fine particles 31 having an average particle diameter of 20 nm was formed with a film thickness of 0.3 μm by an aqueous solution coating method.

In Example 4, a film of Al ₂ O ₃ fine particles 31 having an average particle diameter of 20 nm was formed on each of the surfaces of the metal foils 3a1 and 3b1 where the electrodes 3a2 and 3b2 and the external leads 3a3 and 3b3 were joined by an aqueous solution coating and baking method. .3 μm.

  Each of the above-described mercury-free metal halide lamps 1 according to Examples 1 to 4 and the conventional example was turned on with a lamp power of 35 W, and the life time at that time was measured.

  As is apparent from FIG. 6, each of the mercury-free metal halide lamps 1 according to Examples 1 to 4 has a longer lifetime than the conventional mercury-free metal halide lamp, and the coating films 4a and 4b formed of the fine particles 31. It can be seen that works effectively. It can also be seen that the coating films 4a and 4b in which the acicular particles 51 and the fine particles 31 coexist have a longer life.

In place of the material of each coating film described above, SiO ₂ film, ZrO ₂ film, HfO ₂ film, Y ₂ O ₃ film, Ho ₂ O ₃ film _, Ta ₂ O ₃ film, Al ₂ O ₃ film, Si Also for mercury-free metal halide lamps using ₃ N ₄ film, AlN film, TiN film, Ta film, W film, Re film, Nb film, V film, Zr film, Ho film, Dy film, Y film, and Sc film, respectively. Similarly, it was confirmed that it had good life characteristics.

  FIG. 9 is a front view corresponding to FIG. 2 for explaining a fourth embodiment of the metal halide lamp of the present invention. FIG. 9 also shows the electrode side of one of the lamps, and the other electrode side is the same and is not shown.

  In this embodiment, the coating film 4a includes a region including a joint portion of the metal foil 3a1 with the electrode 3a2, a joint portion of the electrode 3a2 with the metal foil 3a1, and a part of a portion of the electrode 3a2 that does not overlap with the metal foil 3a1. It is formed so as to cover. The region covered with the coating film 4 a of the electrode 3 a 2 extends not only to the portion embedded in the sealing portion 12 a but also to a part of the portion exposed to the discharge space 14.

  In this case, with respect to the distance L from the tip of the electrode 3a2 to the root embedded in the sealing portion 12a of the electrode 3a2, the formation range of the coating film 4a is from the root of the electrode 3a2 to 30% of the distance L. It is considered as a range. In other words, the coating film 4a is not formed between the position of 30% of the distance L from the base of the electrode 3a2 and the tip of the electrode 3a2.

By covering up to a part of the electrode 3a2 exposed to the discharge space 14 with the coating film 4a, it is possible to make the electrode 3a2 difficult to energize, and thus it is possible to suppress the occurrence of back arc. At this time, the coating film 4a is formed of an insulating material having a specific resistance larger than that of the electrode 3a2, in particular, a metal oxide such as SiO ₂ , Al ₂ O ₃ , Sc ₂ O ₃ , Dy ₂ O _3, etc. Can be more reliably suppressed.

  Next, an evaluation result of the mercury-free metal halide lamp according to the fourth embodiment will be described as Example 5.

In Example 6, the thicknesses of the metal foils 3a1 and 3b1 were 25 μm and the length was 10 mm. The electrodes 3a2 and 3b2 were welded to the metal foils 3a2 and 3b2, respectively, and the following coating films 4a and 4b were formed. Further, coating films 4a and 4b of Al ₂ O ₃ fine particles 31 having an average particle diameter of 20 nm were formed with a film thickness of 0.3 μm by an aqueous solution coating and baking method.

  The coverage of the electrodes 3a2 and 3b2 by the coating films 4a and 4b is from the root portion embedded in the sealing portions 12a and 12b of the electrodes 3a2 and 3b2 to 1 mm in the tip direction of the electrodes 3a2 and 3b2 on the discharge space 14 side. did. Except for these conditions, a mercury-free metal halide lamp was manufactured in the same manner as in Example 1 described above.

  In Example 5, a blinking test of a conventional mercury-free metal halide lamp having the same configuration except that the coating films 4a and 4b were not formed was performed at a lamp power of 35W.

  As a result, according to the mercury-free metal halide lamp of Example 5, it was confirmed that the occurrence of back arc was significantly less than that of the conventional example. Further, as to the life characteristics, good results could be obtained as in Examples 1 to 4 in FIG.

  In this embodiment, in addition to extending the lamp life, it is possible to greatly suppress the occurrence of back arc and reduce the occurrence of flickering abnormal discharge.

  FIG. 10 is a schematic configuration diagram for explaining a case where the metal halide lamp according to the present invention is applied to an automotive headlamp. The same reference numerals are given to the same components as those in FIG. The description will focus on the different parts.

  In FIG. 10, the arc tube constituting the main part of the metal halide lamp has a double tube structure, and an inner tube 1 made of, for example, quartz glass is disposed inside the arc tube. The inner tube 1 has an elongated shape in the lamp axis direction, and a substantially elliptical discharge vessel 11 is formed at a substantially central portion thereof. Plate-shaped sealing portions 12a and 12b are formed at both ends of the discharge vessel 11, and cylindrical non-sealing portions 13a and 13b are formed at both ends thereof.

  A socket 7 is connected to the non-sealing portion 13a side of the arc tube. The metal band 71 attached to the outer peripheral surface of the outer tube 9 near the non-sealing portion 13a is connected to the four metal tongue pieces 72 formed on the opening end of the socket 7 on the inner tube 1 holding side. (In FIG. 10, two are shown). And in order to strengthen a connection further, the contact point of the metal band 71 and the tongue piece 72 is welded. A terminal to which a lead wire 3a3 and a support wire (not shown) are connected is formed at the bottom of the socket 7.

  The other ends of the lead wires 3a3 and 3b3 whose one ends are connected to the end portions of the metal foils 3a1 and 3b1 extend outside the sealing portions 12a and 12b along the tube axis. One end of an L-shaped support wire 6 made of nickel is connected to the lead wire 3 b 3 extending to the outside, and the other end extends in the direction of the socket 7. A portion of the support wire 6 parallel to the tube axis is covered with an insulating sleeve 8 made of ceramic.

  Outside the inner tube 1 configured as described above, a cylindrical outer tube 9 in which a metal oxide having an ultraviolet blocking effect is added to quartz glass along the tube axis is provided substantially concentrically with the inner tube 1. It has been. The inner tube 1 and the outer tube 9 are connected by welding the outer tube 9 in the vicinity of the cylindrical non-sealing portions 13a and 13b at both ends of the inner tube 1, and the inner space is airtight. In the space, for example, a rare gas such as nitrogen, neon, argon, xenon, or the like can be sealed or mixed.

  FIG. 11 is a perspective view for explaining a schematic configuration of an embodiment when the metal halide lamp for an automotive headlamp described in FIG. 10 is applied to the automotive headlamp apparatus of the present invention.

  In the figure, reference numeral 111 denotes a reflecting mirror, and 112 denotes a front cover. The reflecting mirror 111 is formed into a deformed paraboloid by molding plastics, and is configured to attach and detach a metal halide lamp (not shown) shown in FIG. 10 from the top rear surface. The front cover 112 is integrally formed with a prism or a lens by molding transparent plastics, and is airtightly attached to the front opening of the reflecting mirror 111.

  FIG. 12 is a circuit diagram for explaining a first embodiment relating to the lighting device of the present invention. In this embodiment, a metal halide lamp is configured to be lit by direct current. In the figure, 121 is a DC power source, 122 is a chopper, 123 is a control unit, R is a lamp current detecting means, VR is a lamp voltage detecting means, 124 is a starting portion, and 125 is a metal halide lamp.

  As the DC power supply 121, a battery or a rectified DC power supply is used. In the case of an automobile, a battery is generally used. However, it may be a rectified DC power source that rectifies AC. If necessary, the electrolytic capacitor C is connected in parallel to perform smoothing.

  The chopper 122 converts the DC voltage into a voltage having a required value and controls the metal halide lamp 125 as required. When the DC power supply voltage is low, a step-up chopper is used, and when it is high, a step-down chopper is used.

  The control unit 123 controls the chopper 22. For example, immediately after the lamp is turned on, a lamp current more than three times the rated lamp current is supplied from the chopper 122 to the metal halide lamp 125, and thereafter, the lamp current is gradually reduced with the passage of time, and is controlled so as to reach the rated lamp current. . In addition, the control unit 123 performs constant power control of the chopper 122 by generating a constant power control signal when a detection signal of the lamp current and the lamp voltage is fed back. Further, the control unit 123 includes a microcomputer in which a temporal control pattern is previously incorporated, and is configured to control the lamp current.

  The lamp current detection means R is inserted in series with the lamp, detects the lamp current, and inputs the control input to the control unit 123. The lamp voltage detection means VR is connected in parallel with the lamp, detects the lamp voltage, and inputs the control voltage to the control unit 23. The starting unit 124 is configured to supply a pulse voltage of 20 kV to the metal halide lamp 125 at the time of starting.

  Then, when the metal halide lamp is DC-lit using the metal halide lamp lighting device of this embodiment, a required light flux is generated immediately after lighting. As a result, it is possible to realize lighting with a luminous flux of 25% and a luminous flux of 80% after 4 seconds 1 second after turning on the power necessary as a vehicle headlamp. Further, since a DC-AC conversion circuit is not required, the cost can be reduced by about 30% compared to AC lighting. Further, the weight can be reduced by 15%. Along with this, the lighting circuit becomes inexpensive.

  FIG. 13 is a circuit diagram for explaining a second embodiment relating to the lighting device of the present invention. The same parts as those in FIG. This embodiment is different in that the metal halide lamp is configured to be AC-lit.

  131 is an alternating current conversion means, and this alternating current conversion means 131 consists of a full bridge inverter. That is, a pair of switching means Q1, Q2 and a series circuit of Q3, Q4 is connected in parallel between the output terminals of the chopper 122 to form a bridge circuit, and the oscillation output of the oscillator 132 is supplied to the four switching means Q1-Q4. The diagonal switching means Q1, Q4 and Q2, Q3 are alternately supplied to generate high-frequency alternating current between the output ends of the bridge circuit.

  The metal halide discharge lamp 125 is turned on by high frequency alternating current. Also in this AC lighting type configuration, the same control as in FIG. 12 is performed.

  According to each embodiment of the lighting device of the present invention of AC and DC, it is possible to light the above-described metal halide lamp of the present invention having excellent life characteristics.

The block diagram for demonstrating 1st Embodiment regarding the metal halide lamp of this invention. The front view which expanded and showed the principal part of FIG. Sectional drawing which expanded and showed the principal part of FIG. The enlarged view for demonstrating 2nd Embodiment regarding the metal halide lamp by this invention. 4 is a cross-sectional view of the main part. Sectional drawing for demonstrating 3rd Embodiment regarding the metal halide lamp by this invention. Explanatory drawing for demonstrating each Example of the coating layer apply | coated to the metal foil of the metal halide lamp of this invention. Explanatory drawing for demonstrating the lifetime of the metal halide lamp by each Example of FIG. The front view for demonstrating 3rd Embodiment regarding the metal halide lamp by this invention. The schematic block diagram for demonstrating the case where the metal halide lamp of this invention is applied to the headlamp for motor vehicles. The perspective view for demonstrating embodiment regarding the headlamp apparatus for motor vehicles of this invention. The circuit diagram for demonstrating 1st Embodiment regarding the lighting device of this invention. The circuit diagram for demonstrating 2nd Embodiment regarding the lighting device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner tube 11 Discharge container 12a, 12b Sealing part 13a, 13b Non-sealing part 14 Discharge space 2 Metal halide 3a, 3b Mount 3a1, 3b1 Metal foil 3a2, 3b2 Electrode 3a3, 3b3 Lead wire 4a, 4b Coating film 31 Fine particles 51 Needle-like particles 6 Support wire 7 Socket 8 Insulating sleeve 9 Outer tube 111 Reflective mirror 112 Front cover 121 DC power supply 122 Chopper 123 Control unit 124 Start unit 125 Metal halide lamp R Lamp current detection means VR Lamp voltage detection means 131 AC conversion means 132 Oscillators Q1-Q4 Switching means

Claims (7)

A discharge vessel having a discharge space and sealing portions provided at both ends of the discharge space;
A discharge medium enclosed in the discharge vessel, comprising a metal halide and a noble gas, and essentially free of mercury;
A pair of electrodes disposed opposite to each other in the discharge space;
Metal foils joined respectively to the base side end portions of the pair of electrodes and hermetically sealed by the sealing portion;
A pair of external leads respectively joined to the other end side of the metal foil and led out of the sealing portion;
A metal halide lamp comprising: a coating film formed of fine particles made of at least one selected from a metal and a metal oxide while covering a region including a joint portion of the metal foil with the electrode.   2. The metal halide lamp according to claim 1, wherein the fine particles forming the coating film include acicular particles.   3. The metal halide lamp according to claim 1, wherein a region where the coating film is formed is on a joint surface side between the metal foil and the electrode.   2. The metal halide lamp according to claim 1, wherein the coating film is formed so as to cover a range including a part of the electrode on a side of a joint portion with the metal foil.   6. The metal halide lamp according to claim 5, wherein the coating film is made of a material having a specific resistance larger than that of the electrode. A metal halide lamp according to any one of claims 1 to 5,
A lighting device comprising: a lighting circuit for lighting the metal halide lamp with a direct current. A metal halide lamp according to any one of claims 1 to 5,
An automotive headlamp device comprising: a main body of an automotive headlamp device, wherein the metal halide lamp is disposed and has an optical axis along a longitudinal direction of the discharge vessel of the metal halide lamp.

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