JP2008077891A - Metal halide discharge lamp, metal halide discharge lamp lighting device and lighting device - Google Patents

Abstract

【Task】
Provided are a metal halide discharge lamp for direct current lighting suitable for a vehicle headlamp that is compact and suppresses occurrence of cracks in a sealing portion on the anode side, and a metal halide discharge lamp lighting device and an illumination device including the metal halide discharge lamp.
[Solution]
The metal halide discharge lamp MHL is connected to the hermetic container 1 having a surrounding portion 1a and a pair of sealing portions 1b in which a sealing metal foil is embedded in an airtight manner, and a base end connected to the sealing metal foils 3A and 3B. The anode 2A and the cathode 2K, the electrode main part being desired to be separated and opposed in the surrounding part, and the intermediate part supported by the sealing part, the pair of current introduction conductors 4A and 4B, the first halide and the second A discharge medium containing a halide and a rare gas and essentially free of mercury, the direction of the current flowing in the hermetic vessel is always a single direction that does not change with time, and the anode side sealing metal The length of the foil is larger than the length of the sealing metal foil on the cathode side, and the length is 10 to 19 mm.
[Selection] Figure 2

Description

  The present invention relates to a discharge lamp, in particular, a mercury-free metal halide discharge lamp, a metal halide discharge lamp lighting device, and an illumination device for automobile headlamps.

In recent years, HID lamps have been widely applied particularly in the field of outdoor lighting because of their high efficiency and long life. Among these, metal halide lamps have good color rendering properties and are taking advantage of the characteristics to be spreading not only in the field of outdoor lighting but also in the field of indoor lighting, and are attracting attention as light sources for video equipment and light sources for vehicle headlamps.

  In addition, by encapsulating a metal halide selected from a specific group as a lamp voltage forming substance, mercury can be obtained with almost the same electrical and luminous characteristics as encapsulating mercury without encapsulating mercury. Free metal halide lamps (hereinafter referred to as “mercury-free lamps” for the sake of convenience) are known (see Patent Document 1). This type of mercury-free lamp has been put into practical use since July 2004 as an automotive headlamp.

  Mercury-free lamps are environmentally friendly because they do not contain mercury. They also have advantages such as good spectral start-up characteristics at start-up, suitable for dimming, and small variations in characteristics. Is expected to spread. In such a mercury-free HID lamp, when the rare gas is set to 1 atm or higher, it is preferable in terms of efficiency, maintenance of lamp voltage, good start-up characteristics, and easy arc transition.

  By the way, both the conventional metal halide discharge lamps containing mercury (hereinafter referred to as “mercury-containing lamps” for convenience) and the above-described practical mercury-free lamps are designed to be lit with an alternating current lighting system. It is configured.

  However, when a metal halide discharge lamp used for an automotive headlamp is lit using an AC lighting circuit, the current supplied from the power source is DC, so a DC-AC conversion circuit must be interposed in the lighting circuit. Don't be. A full-bridge inverter circuit is generally used as the DC-AC conversion circuit. Since this full bridge circuit uses a relatively large semiconductor switching element, the cost is increased and the lighting circuit is increased in size as compared with the DC lighting system. In other words, if the mercury-free lamp can be lit by the direct current method, the cost and size of the lighting circuit can be reduced.

  Also, the direct current disappears and there is less flickering. That is, for example, in the case of alternating current lighting and rectangular wave lighting, the current crosses the zero point when the polarity is switched. At this time, since the mercury-free lamp does not have the effect of absorbing free iodine by mercury (production of mercury iodide), the lamp voltage is rapidly increased, and the lamp is likely to flicker, and is likely to be extinguished. These points are improved by direct current lighting. For the same reason, DC lighting is more resistant to vibration. That is, for example, when the lamp is subjected to strong vibration in the case of alternating current lighting and rectangular wave lighting, the electrical characteristics suddenly evaporate due to the rapid evaporation of halide or other discharge medium in the arc tube. Easier to disappear and easily disappears.

  Furthermore, when a halide such as rare earth metal or Sc that easily reacts with quartz, which is the arc tube material, or a halide of Na that easily escapes quartz, is encapsulated, the white turbidity of the arc tube and Na loss are caused by AC. However, DC is generally less. In the case of direct current, since the electric field is unidirectional and metal elements (such as Sc and Na) are attracted to the cathode, the arc tube tends to become cloudy or Na is lost on the cathode side, but these phenomena occur on the anode side. There are few. As a result, generally speaking, direct current causes less clouding of the arc tube and lack of Na.

  Furthermore, in the mercury-free lamp, it is possible to suppress a change in chromaticity at the time of dimming as seen in a mercury-containing lamp. In a mercury-containing lamp, when the light is adjusted from the rated lamp power, that is, the total light state, mercury having a vapor pressure higher than that of the main light emitting material emits light relatively strongly, and chromaticity changes. By making mercury free, the chromaticity change is much less. However, in the AC lighting system, since there is a polarity change point, it is easy for the light to disappear during dimming. That is, the mercury-free lamp can be dimmed, but the range in which the dimming can be dimmed is wider than the alternating current.

  Furthermore, when the mercury-containing lamp is lit with a direct current, the enclosed metal, such as Sc, Na, or rare earth metal, is positively charged (ionized) in the arc tube, so that it is drawn to the cathode. As a result, Sc, Na, Although light emission of rare earth metals can be obtained, light emission of these metals decreases on the anode side, causing a phenomenon in which only mercury is emitted. For this reason, the light color is different between the anode side and the cathode side of the arc tube (color separation), and the proportion of low-efficiency mercury emission increases, so the light efficiency of the lamp decreases. In the case of mercury-free lamps, this tendency is alleviated.

  As described above, in the mercury-free lamp, direct current lighting is preferable to alternating current lighting, but there are the following problems.

  That is, in the discharge lamp, electrons are struck by the anode, so that the anode is heated to a higher temperature than the cathode in order to absorb the energy of the electrons. For this reason, the anode side becomes stricter in terms of temperature. As an improvement measure for the electrode, there is a method of changing the dimensions of the tip and the shaft. In other words, since the shaft portion is sealed with quartz, particularly when flashing is intense as in an automobile headlamp, the larger the shaft diameter is, the more the flashing cannot be endured. On the other hand, the tip is preferably large in size in order to reduce the electrode temperature. Therefore, it is known as an improvement measure to increase the size of the tip portion relative to the shaft portion, or to make the tip portion spherical with a diameter larger than that of the shaft portion (tip spherical electrode).

  The adverse effect of the high temperature on the anode side becomes conspicuous at the junction between the sealed metal foil and the current introduction conductor. The heat from the anode is conducted from the tip portion to the current introduction conductor through the shaft portion, the joint portion between the shaft portion and the sealing metal foil, and further through the sealing metal foil. By the way, the junction between the current introduction conductor and the sealing metal foil is sealed to the sealing portion but communicates with the atmosphere. That is, the current introduction conductor cannot be hermetically sealed to quartz. For this reason, when the junction between the current introduction conductor and the sealing metal foil is in a high temperature state (350 ° C. or higher), it is gradually oxidized. Oxidation of the sealing metal foil exerts stress on the surrounding quartz, resulting in cracking of the quartz in the sealing portion, and eventually the lamp leaks and becomes unsatisfactory. In order to lower the temperature of the junction between the current introduction conductor and the sealing metal foil, it should be first considered to keep the distance from the anode as the heat source.

  However, there are various dimensional limitations in lamps that are important to be compact in relation to the lamp, and these limiting conditions must also be considered. For example, a mercury-free HID lamp for an automotive headlamp, in which compactness is important, has a structure as shown in FIG. In terms of dimensions, the distance from the reference surface of the base to the optical center is defined as 27.1 mm. In addition, from the relationship with the lamp, a maximum of about 50 mm is preferable from the reference surface to the lamp tip.

  For the above reasons, there is a problem in selecting whether the anode is the base side or the opposite side in FIG. In this regard, a mercury-free HID lamp is known in which a base that makes electrical contact with an external socket is disposed on the anode side (see Patent Document 2). In patent document 2, it is going to improve the temperature condition in the said sealing part by transmitting the heat | fever of the sealing part by the side of an anode to a nozzle | cap | die.

  The advantage of using the anode side as the base side is that the dimensions can be controlled. In other words, the dimensional limit is greater when the temperature-strict anode side is opposite to the base. That is, since the optical center is 27.1 mm from the reference surface of the base and the lamp tip is 50 mm from the reference surface of the base, the distance from the optical center to the lamp tip is only about 23 mm. In order to increase the distance from the anode, which is a heat source, to the junction between the sealed metal foil and the current introduction conductor, it is necessary to increase the length of the sealed metal foil. In addition, when the holding part of the electrode shaft part by the quartz glass of the sealing part is lengthened, when the flashing is severe like an automobile headlamp, the quartz glass near the electrode shaft in the holding part of the electrode is cracked (shaft crack). ) And easily become a disadvantage.

  On the other hand, in a light source device configured for a projection display device in which a discharge lamp is incorporated in a concave mirror and integrated with each other, a metal foil embedded in a sealing portion of the discharge lamp located on the opening side of the concave mirror Is longer than the metal foil of the sealing part located on the top side of the concave mirror on the base side (see Patent Document 3). However, when it is required to be compact, such as a metal halide discharge lamp for automobile headlamps, increasing the length of the sealing metal foil can meet the above-mentioned size limitation of the sealing portion. It is easy to lose.

JP 11-238488 A JP 2000-106133 A JP-A-2005-072013

  However, mercury-free HID lamps for automotive headlamps require much better flashing characteristics than general lighting lamps. That is, it is necessary to blink the lamp frequently in the use of the headlamp. Approximately 12,000 flashing lifetimes are required during a typical lifetime (2000 hours).

  In addition, for headlamps, it is important that the luminous flux rises quickly. Therefore, when starting the circuit, a lamp power more than twice that of the steady state is applied to the lamp, and then the current is gradually reduced. Is common. That is, in the case of a lamp power of 35 W at steady state, an input power of 75 W is applied at the start. Due to such frequent flashing with a heavy load on the lamp, the two types of quartz cracks tend to make the lamp unsatisfactory. The first is when the quartz near the electrode axis cracks and expands (electrode axis crack), and the second is when the quartz near the sealing metal foil cracks and expands (foil crack). It is. In the case of direct current lighting, since the temperature environment on the anode side is severe, problems caused by cracks at the time of blinking are overwhelmingly generated on the anode side.

  The present inventor defines the length of the sealing metal foil on the anode side within a predetermined range, so that it is compact like a metal halide discharge lamp for an automobile headlamp, and at the same time, The inventors have found that it is possible to effectively suppress the occurrence of cracks, and have reached the present invention.

  In addition, the occurrence of the above-mentioned two cracks on the anode side is related to the product L · Q of the length (L) of the sealing metal foil on the anode side and the lamp current (Q) in the steady state. I found it. That is, the electrode and the sealing metal foil are joined. When blinking is performed, the joined body of the electrode and the sealing metal foil applies stress to the quartz centering on the joint. In the region where L · Q is small, the stress applied to the quartz in the electrode portion is dominant, and electrode shaft cracks are likely to occur. In the region where L · Q is large, the stress applied to the quartz of the sealing metal foil is dominant, and foil cracks are likely to occur. Therefore, there are suitable areas of L · Q regarding the blinking characteristics.

  The present invention is suitable for an automotive headlamp that effectively suppresses the occurrence of cracks in the sealing portion on the anode side while being compact by setting the length of the sealing metal foil on the anode side within a predetermined value range. An object of the present invention is to provide a metal halide discharge lamp for direct current lighting, a metal halide discharge lamp lighting device including the same, and a lighting device.

  The metal halide discharge lamp according to the present invention is a fire-resistant and translucent light source having an enclosed portion in which a discharge space is formed and a pair of sealed portions in which a sealing metal foil is embedded in an airtight manner. A gas-tight airtight container; each base end is connected to a sealing metal foil embedded in the sealing portion of the airtight container, the electrode main portion at the tip is desired to be spaced apart from the surrounding portion, and the middle portion is the sealing portion An anode and a cathode supported by and sealed in an airtight container; a pair of currents whose leading ends are connected to a sealing metal foil embedded in a pair of sealing portions and whose other ends are exposed to the outside from the sealing portions An introduction conductor; and a first halide, a second halide, and a rare gas enclosed in an airtight container, wherein the first halide is a group consisting of sodium (Na), scandium (Sc), and a rare earth metal One kind selected from A plurality of types of halides, the second halide being magnesium (Mg), iron (Fe), cobalt (Co), chromium (Cr), zinc (Zn), nickel (Ni), manganese (Mn), From aluminum (Al), antimony (Sb), beryllium (Be), rhenium (Re), gallium (Ga), titanium (Ti), zirconium (Zr), hafnium (Hf), tin (Sn) and indium (In) A discharge medium which is one or more metal halides selected from the group consisting essentially of mercury-free discharge medium, and the direction of the current flowing in the hermetic vessel does not change with time. And the length of the anode-side sealing metal foil is larger than the length of the cathode-side sealing metal foil, and the length is 10 to 19 mm. It is.

  According to the present invention, the discharge medium is mercury-free, and the anode-side sealed metal foil has a length in a predetermined range as compared with that on the cathode-side, whereby the anode-side current introduction conductor and the sealed metal foil To provide a metal halide discharge lamp that is compact, has good flashing characteristics and has a long life, and a metal halide discharge lamp lighting device and an illumination device including the metal halide discharge lamp. Can do.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[About the first form]
1 and 2 show a first embodiment for carrying out the metal halide discharge lamp of the present invention, FIG. 1 is a front view, and FIG. 2 is an enlarged plan view of an arc tube.

  In the present invention, the metal halide discharge lamp MHL includes an airtight container 1, an anode 2A, a cathode 2K, a pair of current introduction conductors 4A and 4B, and a discharge medium (not shown) as shown in the drawings.

  In the illustrated embodiment, as another additional configuration, an arc tube IT is configured by the airtight container 1, the anode 2A, the cathode 2K, the pair of current introduction conductors 4A and 4B, and the discharge medium. An outer tube OT for storing IT inside, an insulating tube T and a base B are provided to constitute a metal halide discharge lamp MHL for an automobile headlamp.

  Hereafter, each said component is demonstrated.

[About arc tube IT]
(Regarding the airtight container 1) The airtight container 1 is fireproof and translucent, and is made of quartz glass in this embodiment, and includes an enclosing portion 1a and a pair of sealing portions 1b. The surrounding part 1a is hollow, and the hollow part becomes the discharge space 1c. The internal volume of the discharge space 1c can be appropriately set according to the use of the metal halide lamp, but is generally 0.1 cc or less as a small metal halide lamp suitable for applying the present invention. In the case of a headlamp, it is preferably 0.05 cc or less.

  The discharge space 1c can have an arbitrary shape such as a substantially cylindrical shape, a spherical shape, or an elliptical spherical shape. In the case of a headlamp, it preferably has a substantially cylindrical shape. On the other hand, the outer surface of the surrounding part 1a of the translucent airtight container 1 has a rotating quadratic curved surface shape such as an elliptical shape or a spindle shape. Therefore, the wall thickness of the surrounding portion 1a is generally the largest in the central portion in the tube axis direction and gradually decreases in both end directions.

  Moreover, the preferable size of the enclosure part 1a in the airtight container 1 as the metal halide discharge lamp MHL for motor vehicle headlamps, and the discharge space 1c formed in the inside is as follows. That is, the length of the surrounding portion 1a in the tube axis direction is 7.4 to 8.2 mm, the inner diameter of the discharge space 1c is 2.2 to 2.9 mm, the outer diameter is 5.6 to 6.9 mm, and the wall thickness is 1 0.7 to 2.5 mm, and the internal volume of the discharge space 1c is 20 to 35 μl.

  Furthermore, the airtight container 1 is “translucent and fire-resistant” means that at least a light guide portion that is a portion to emit light to the outside of the surrounding portion 1a is translucent, and This means that it has at least heat resistance enough to withstand the normal operating temperature of the metal halide lamp MHL. If necessary, it is allowed to form a halogen-resistant or halogen-resistant transparent coating on the inner surface of the enclosure 1a of the hermetic container 1 or to modify the inner surface of the hermetic container 1.

  The pair of sealing portions 1b and 1b are formed integrally with the surrounding portion 1a adjacent to the surrounding portion 1a. In this embodiment, a pair of sealing portions 1b can be formed so as to extend to both ends of the surrounding portion 1a in the tube axis direction. The sealing portion 1b seals the surrounding portion 1a, and the base end portions of an anode 2A and a cathode 2K described later are embedded therein. In order to realize this, sealing metal foils 3A and 3B, which will be described later, are embedded in an airtight manner in the pair of sealing portions 1b and 1b. Further, the pair of sealing portions 1b and 1b extend integrally from both ends of the surrounding portion 1a along the tube axis direction.

  In the present invention, the pair of sealing metal foils 3A and 3B are defined so that the length is within a predetermined range. In other words, the sealing metal foil 3A is airtightly embedded in the sealing portion 1b in order to be bonded to an anode 2A described later and seal the surrounding portion 1a. In addition, in order to be able to supply power between the anode 2A and the cathode 2K from an unillustrated lighting circuit which is preferably digitized, a shaft portion of the anode 2A is provided at one end of the sealing metal foil 3 on the side of the surrounding portion 1a. The base end portion is connected to the other end portion, and a current introducing conductor 4A described later is connected to the other end portion. Similarly, the base end portion of the shaft portion of the cathode 2K is connected to one end portion of the other sealing metal foil 3 on the surrounding portion 1a side, and a current introduction conductor 4B described later is connected to the other end portion. In addition, the said connection can be performed by welding, for example. The thickness of the sealing metal foils 3A and 3B is not particularly limited in the present invention, but is generally 50 μm or less.

In the present invention, the sealing metal foil 3A on the anode 2A side has a length L _A in the tube axis direction, as shown in FIG. 2, and the length L _{K in} the tube axis direction of the sealing metal foil 3B on the cathode 2K side. It is larger and 10-19 mm. When the length L _A of the sealed metal foil 3A is less than 10 mm, since the cracks occur in the sealing portion of the anode side becomes short-lived, it is impossible. Further, when the length _{L A} of the sealed metal foil 3A is a 19mm greater, since it is impossible to the light center distance 27.1Mm, it is impossible. In addition, it is 12-16 mm suitably. If it is this range, it is effective with respect to the crack suppression of a sealing part, and the compactness of a lamp | ramp.
It becomes easy to secure the optical center distance with a comparative margin while sufficiently suppressing the temperature rise of the sealing metal foil.

  Further, the material of the sealing metal foil 3 is not particularly limited. For example, molybdenum (Mo) or rhenium-tungsten alloy (Re-W) can be used.

  Furthermore, the method of embedding the sealing metal foil 3 in the sealing portion 1b is not particularly limited, but, for example, a reduced pressure sealing method, a pinch sealing method, or the like can be employed alone or in combination. In the case of a metal halide lamp used for a headlamp or the like in which a rare gas such as xenon (Xe) is enclosed at 5 atm or more at room temperature with a small inner volume of the surrounding portion 1a of 0.1 cc or less, the latter is preferable.

  Then, the pair of sealing metal foils 3A and 3B seals the airtight container 1 by having the intermediate portion in the tube axis direction in close contact with the sealing portion 1b by the melting of the quartz glass of each sealing portion 1b. .

    (Anode 2A and Cathode 2K) The anode 2A is composed of an anode main part A1 and a shaft part A2. The anode main portion A1 is a tip portion exposed to the discharge space 1c of the anode 2A, and heat generation is remarkable due to the inflow of electrons that occupy most of the lamp current, and thus a structure that easily radiates heat is adopted. For example, it swells in a spherical or cylindrical shape, or is configured by winding a coil around the tip of the shaft portion A2, and has a structure in which the surface area is large and heat dissipation is promoted. The maximum diameter of the anode main part A1 is preferably 0.50 to 0.70 mm.

  The shaft portion A2 is in charge of the intermediate portion and the base end portion of the anode 2A. The intermediate portion is loosely supported (held) by the sealing portion 1b, and the base end portion is connected to the sealing metal foil 3A, so that the sealing portion 1b is configured to be relatively thin so that cracks are unlikely to occur. . In addition, when anode main part A1 is the said numerical range, axial part A2 is good to set it as a diameter of 0.25-0.40 mm.

  The cathode 2K includes a cathode main portion K1 and a shaft portion K2. The cathode main portion K1 is a tip portion exposed to the discharge space 1c of the cathode 2K, and the tip is formed in a hemispherical shape or a conical shape as desired so as to easily emit electrons and to stabilize the position of the cathode bright spot. Can do. The shaft portion K2 is in charge of the intermediate portion and the base end portion of the cathode 2K. And since an intermediate part is loosely supported (clamped) by the sealing part 1b and a base end part is connected to the sealing metal foil 3B, it is comprised comparatively thinly so that a crack may not arise.

  Further, the shaft portion K2 of the cathode 2K is preferably set to an appropriate value within a diameter range of 0.25 to 0.40 mm. And although it is common to comprise with a single refractory metal, it may be comprised by joining different refractory metals if desired.

  Furthermore, the anode 2A and the cathode 2K are formed of a refractory metal selected from the group such as tungsten (W), doped tungsten, thorium tungsten, rhenium (Re), and tungsten-rhenium alloy (W-Re) in this embodiment. be able to. In particular, for the cathode 2K, it is effective to use thorium tungsten having good electron emissivity, doped tungsten doped with an electron emissive metal or an oxide thereof, or the like.

  Furthermore, the length of the portion inserted into the sealing portion 1b of the shaft portions A2 and K2 of the anode 2A and the cathode 2K, that is, the length from the boundary between the surrounding portion 1a and the sealing portion 1b to the foil end is 3 to 7 mm. It is preferable from the viewpoint of preventing foil cracks and axial cracks.

  By the way, in FIG. 1, after forming the sealing portion 1b on the left anode 2A side, the sealing tube 1d is integrally removed from the outer end portion of the sealing portion 1b without being cut off, and a base B, which will be described later. It extends in.

    (About the current introduction conductors 4A and 4B) In the present invention, the current introduction conductors 4A and 4B are welded to the other ends of the sealing metal foils 3A and 3B in the sealing portions 1b at both ends of the airtight container 1, The proximal end side is led out to the outside.

  In FIG. 1, a cathode 2K-side current introduction conductor 4B led to the right from the light-emitting tube IT is folded back along an outer tube OT (to be described later) and introduced into a base B (to be described later) to the side edge side. It is connected to one cap terminal t1 located. On the other hand, in FIG. 1, the current introduction conductor 4B on the anode 2A side led out from the arc tube IT to the left extends in the sealing tube 1d along the tube axis and is introduced into the base B. And connected to the other cap terminal (not shown) located on the center side.

  In addition, although the material of the current introduction conductors 4A and 4B is not particularly limited in the present invention, for example, molybdenum (Mo), tungsten (W), Kovar (Fe—Ni—Co alloy), or the like can be used.

    (Regarding Discharge Medium) The discharge medium contains first and second halides and a rare gas.

  The first halide is a medium that mainly emits visible light, and is mainly composed of one or more halides selected from the group consisting of at least sodium (Na), scandium (Sc), and rare earth metals. Mercury is essentially not contained, but it can be contained if it is as small as impurities.

  The second halide is an effective medium mainly for forming a lamp voltage, and includes magnesium (Mg), iron (Fe), cobalt (Co), chromium (Cr), zinc (Zn), nickel (Ni ), Manganese (Mn), aluminum (Al), antimony (Sb), beryllium (Be), rhenium (Re), gallium (Ga), titanium (Ti), zirconium (Zr), hafnium (Hf), tin (Sn) ) And indium (In). One or more metal halides selected from the group consisting of indium (In).

  The rare gas acts as a starting gas and a buffer gas, and one or a plurality of kinds such as argon (Ar), krypton (Kr), and xenon (Xe) can be used. In the case of a mercury-free lamp, sealing a rare gas at 1 atm or more is effective in terms of luminous efficiency, lamp voltage maintenance, good luminous flux rise characteristics, and ease of glow-arc transition. Furthermore, as a metal halide lamp MHL for automobile headlamps, in order to further improve the light color rise characteristics and the luminous flux rise characteristics, xenon is 5 atm or more, preferably 7 to 18 atm, and more preferably 8 x. It is preferable to enclose in a range of ˜13 atm or so that the pressure in the internal space at the time of lighting is 50 atm or more. Thereby, when the vapor pressure of the luminescent metal immediately after the start is low, white light emission of Xe can be contributed as a luminous flux at the time of startup.

  As the type of halogen constituting the halide, iodine is most suitable among the halogens in terms of reactivity, and at least the main light emitting metal is mainly encapsulated as iodide. However, if necessary, different halogen compounds such as iodide and bromide can be used in combination.

  [Outer tube OT] In the present invention, the metal halide lamp MHL is allowed to include the outer tube OT as desired. The outer tube OT is made of quartz glass, high silicate glass, or the like, and is a means for housing at least the main part of the arc tube IT therein. Then, UV rays radiated from the arc tube IT to the outside are blocked, mechanically protected, and touching the translucent airtight container 1 of the arc tube IT with a hand, it is attached to human fingerprints and fat and is devitrified. Prevent the cause or keep the translucent airtight container 1 warm.

  Further, the inside of the outer tube OT may be hermetically sealed against the outside air according to the purpose, or an inert gas may be enclosed. In this embodiment, nitrogen is sealed at 0.1 atm.

  Further, a light shielding film can be provided on the outer surface or the inner surface of the outer tube OT.

  In the illustrated embodiment, when the outer tube OT is formed, the outer tube OT is made transparent by glass-welding both ends thereof to sealing portions extending in the tube axis direction from both ends of the translucent airtight container 1. It can comprise so that it may support with the airtight container 1. FIG. The outer tube OT has an ultraviolet ray cutting performance, accommodates the arc tube IT therein, and the diameter-reduced portions 5 at both ends are welded to the sealing portion 1b of the arc tube IT. However, the inside is not airtight but communicates with the outside air.

  [Insulating tube T] The insulating tube T is made of ceramics, and the insulating tube T is made of a heat-resistant insulator such as ceramics and covers a portion extending in parallel with the arc tube IT of the current introduction conductor 4B. is doing.

  [About Base B] In the present invention, the metal halide lamp MHL is allowed to include the base B as desired. The base B is a means that functions to connect the metal halide lamp MHL to a lighting circuit (not shown) or to mechanically support the metal halide lamp MHL. In the illustrated form, the base B is standardized for an automobile headlamp. The arc tube IT and the outer tube OT are planted and supported along the central axis, and are configured to be detachably mounted on the rear surface of the automobile headlamp.

  Further, since the base B supports the sealing portion 1b on the anode 2A side of the arc tube IT through the sealing tube 1d, the sealing metal foil 3A on the anode 2A side is close to the base B. Be placed.

  Furthermore, although not shown in FIG. 1, it is preferable that the joint between the sealing metal foil 3 </ b> A and the current introduction conductor 4 </ b> A is located in the base B because the cooling effect is further improved.

  It is the lamp | ramp structure shown in FIG.

Airtight container: Quartz glass, the surrounding part is spheroid,
Inner diameter 2.6mm in the short axis direction perpendicular to the tube axis
Sealing metal foil 3A on the anode side is 20μm thick, 1.7mm wide, 14mm long
Sealing metal foil 3B on the cathode side is 20μm thick, 1.7mm wide, 7mm long
Anode: Made of doped tungsten, the anode main part is a sphere with a diameter of 0.65 mm,
Shaft part is 0.35mm in diameter, 7mm in length, embedded length of sealing part is 5mm
Cathode: Made of triated tungsten containing 0.1 mass% tria,
Cathode main part and shaft part have the same diameter, diameter 0.35mm, length 7mm, sealing part embedded length 5mm
Distance between electrodes: 4.2mm
Discharge medium: ScI ₃ -NaI-ZnI ₂ (0.10-0.25-0.12mg), Xe11 atmospheres Rated lamp power: 35W
Life characteristics: Can be lit even after 5000 hours of life test

The life test was performed using a cycle of direct current lighting for 1 hour and light extinction for 10 minutes.

[Comparative Example 1]

Airtight container: Sealed metal foils 3A and 3B on the anode and cathode sides are both 7mm long
Other specifications are the same as in the first embodiment.

Life characteristics: Life test for 10 metal halide discharge lamps of Comparative Example 1
As a result, all lamps oxidized and cracked within 1000 hours.
It became a disadvantage.

  In the case of Comparative Example 1, in any lamp, a crack was generated in the vicinity of the junction between the sealed metal foil on the anode side and the current introduction conductor, the airtightness was broken, and the lamp was not turned on. When observed in detail, the sealing metal foil 3A gradually turns black from the current introduction conductor 4A. As a result of analysis, it was found that it was oxidized.

On the other hand, the sealing metal foil on the cathode side did not show oxidation phenomenon and crack generation.
[Comparative Example 2]

  A mercury-free lamp in practical use (same specifications as in Example 1 except that the pair of electrodes has the same symmetrical structure as the cathode in Example 1) was subjected to rectangular wave AC lighting.

Life characteristics: Oxidation and cracks do not occur even after 5000 hours of life test.
It was possible to light up.

  Next, in the metal halide discharge lamp of Example 1, the results of investigating the influence on the life characteristics when the length of the anode-side sealed metal foil 3A is changed will be described with reference to Table 1. Although the length of the sealing portion 1b on the anode 2A side changes according to the length of the sealing metal foil 3A, other specifications are fixed. Each lamp was tested in triplicate.

Table 1 is a table showing the results of a life test when the length of the anode-side sealed metal foil 3A was variously changed in Example 1. In the table, the lamp No. Indicates lamps with different length specifications of the anode-side sealing metal foil 3A. A life test was conducted on a metal halide lamp using a DC lighting circuit. The length of the sealing metal foil is L _A (mm) indicating the length of the sealing metal foil 3A on the anode 2A side, and L _K (mm) is the length of the sealing metal foil 3B on the cathode 2K side.

As can be understood from Table 1, as long as the length L _A (mm) of the sealing metal foil 3A on the anode 2A side is in the range of 10 to 19 mm as in the lamps 3 to 12, the same 5000 hours as described above. The metal halide discharge lamp can be turned on even after the life test, and a metal halide discharge lamp that satisfies the standard of an optical center distance of 27.1 mm can be obtained.

  However, in the case of the lamp 13, the life test word for 5000 hours can be lit, but if the sealing metal foil 3A is 20 mm or more, it becomes impossible to set the distance of the optical center to 27.1 mm.

On the other hand, in the case of the lamps 1 and 2 in which the length L _A (mm) of the sealing metal foil 3A is less than 10 mm, the vicinity of the junction between the sealing metal foil 3A and the current introduction conductor 4A within 5000 hours. Cracks were generated in the quartz glass, and the hermeticity of the hermetic container 1 was broken, resulting in inconvenience. This phenomenon was reproducible. In this case, the sealing metal foil 3A on the anode 2A side gradually turned black. As a result of analyzing the discolored portion, it was found that the sealing metal foil 3A was oxidized. From this, it can be seen that the sealing metal foil 3A had a temperature during lighting of 350 ° C. or higher. In addition, in the sealed metal foil 3B on the cathode 2K side, inconveniences such as oxidation and cracks were not generated.

Next, as Example 2, the length of the sealed metal foil 3A on the anode 2A side was variously changed in the same manner as in Table 1, and the metal halide discharge was made to have the same specifications as in the example except that the cathode 2K was arranged on the base B side. The result of manufacturing a lamp and performing a life test will be described with reference to Table 2. In Table 2, description of the same parts as in Table 1 is omitted.

As can be understood from Table 2, in the case of Example 2, when the length L _A (mm) of the sealing metal foil 3A on the anode 2A side becomes 10 mm or less, it becomes unsatisfactory, and when the lamp 9 becomes 16 mm or more, 5000 hours. Although it can be turned on later, if the distance from the base reference surface to the tip of the lamp is within 50 mm, the optical center distance becomes out of specification. However, the effect of the present invention can be achieved when the length L _A (mm) of the sealing metal foil 3A on the anode 2A side is in the range of 11 to 15 mm. From this and comparison with FIG. 3, in the present invention, in addition to increasing the length L _A (mm) of the sealing metal foil 3A on the anode 2A side within a predetermined range, the sealing on the anode 2A side is also performed. It turns out that it is much more effective to arrange the metal-fitted metal foil 3A on the base B side.

Discharge medium: ScI ₃ -NaI-MnI ₂ (0.10-0.25-0.15 mg), Xe11 atmosphere Others are the same as in Example 1.

  In Example 3, the material of the second halide was changed. A metal halide discharge lamp similar to that in Example 1 was manufactured, and a life test was performed in the same manner as in Tables 1 and 2. As a result, almost the same results as in FIGS. 3 and 4 were obtained.

Discharge medium: NdI ₃ —NaI—ZnI ₂ (0.10-0.25-0.12 mg), Xe11 atm.

  In Example 4, the first halide was changed. A metal halide discharge lamp similar to that in Example 1 was manufactured, and a life test was performed in the same manner as in Tables 1 and 2. As a result, almost the same results as in Tables 1 and 2 were obtained.

Next, the 2nd form for implementing the metal halide discharge lamp of this invention is demonstrated. In this embodiment, the metal halide discharge lamp MHL has a length of the sealing metal foil 3A embedded in the sealing portion 1b on the anode 2A side as L _A (mm), and a lamp current Q (A) during steady lighting and when, _equation: 7.36 <is configured so as to satisfy L a · Q <15.12.

Discharge medium: ScI ₃ -NaI-ZnI ₂ (eight kinds of 0.10-0.25-ZnI ₂ are set), Xe11 atmospheric pressure, etc.

Since the amount of ZnI ₂ is related to the lamp voltage, the metal halide discharge lamps A to H in which the amount of ZnI ₂ encapsulated was changed to 8 types had a lamp voltage of 38 to 52 V at 35 W input.
For example, when 0.12 mg of ZnI _{2 was} enclosed, the lamp voltage was 42 V (lamp F). In this case, the product L _A · Q of the length L _A (mm) of the sealing metal foil 3A and the lamp current Q (A) was as shown in the numerical values in the table shown in FIG.

In Table 3, the uppermost row is the length of the sealed metal foil (mm) on the anode side, which is divided from 6 mm to 24 mm from the left column to the right column. Further, each of the lamp voltage from the second stage to the lowermost stage indicates the value of L _A · Q at different each lamp A~H from above.

As can be seen from Table 3, the closed area surrounded by a thick frame is the flashing life test.
The L _A · Q value in the combination of the anode-side sealed metal foil length and the lamps A to H that has achieved 12,000 or more blinks is shown. In other words, the first metal halide discharge lamp of the mercury-free in form of the invention, the product of the sealed metal foil length and lamp current formula: 7.36 satisfies _<L A · Q <15.12 range If it is within, it means that the flashing life is prolonged in addition to the generation of cracks.

    FIG. 3 is a circuit block diagram of one embodiment for implementing the metal halide discharge lamp lighting device of the present invention. That is, the metal halide discharge lamp lighting device includes the above-described metal halide discharge lamp 13 of the present invention and a DC electronic lighting circuit that supplies a current whose polarity does not change with time to light the metal halide discharge lamp. In the illustrated embodiment, the DC electronic lighting circuit includes a DC main lighting circuit 12A and a starter 12B. The DC main lighting circuit 12A is configured as described later, and can be attached to the headlamp body 11 described later.

  The metal halide discharge lamp 13 is a metal halide discharge lamp of the present invention shown in FIG.

  The DC main lighting circuit 12A is constituted by a DC electronic circuit mainly including a boosting chopper and the like, and boosts the DC power supply voltage in a controllable manner so as to obtain a desired DC output voltage and applies it to the metal halide discharge lamp 13. The DC power supply voltage can be obtained from a DC power supply DC such as a battery power supply or a rectified DC power supply.

  The starter 12B outputs a high voltage pulse when the metal halide discharge lamp 13 is started, applies it to the metal halide discharge lamp 13, and instantly starts it.

  Thus, in the metal halide discharge lamp lighting device, the DC main lighting circuit 12A starts the metal halide discharge lamp 13 and lights it stably. In addition, as a metal halide discharge lamp lighting device for automobile headlamps, the metal halide discharge lamp 13 is started, and immediately after the start of lighting, power more than twice the rated lamp power is continuously supplied for several seconds, and then a halide. The metal halide discharge lamp 13 is set so that the lamp power is reduced at a constant ratio when the lamp rapidly evaporates, and then the lamp is gradually reduced from the large value to the rated lamp power while gradually decreasing to a rated lamp power. Operates to light up while controlling.

    FIG. 4 is a schematic diagram showing an automobile headlamp as an embodiment for carrying out the lighting device of the present invention. In the figure, 11 is a headlamp body, 12A is a DC main lighting circuit, 12B is a starter, and 13 is a metal halide discharge lamp.

  In the present invention, the headlamp body 11 refers to the remaining part of the headlamp excluding the metal halide discharge lamp 13, the DC main lighting circuit 12A, and the starter 12B. The headlamp body 11 has a container shape, and includes a reflecting mirror 11a inside, a lens 11b on the front surface, and a lamp socket not shown.

The front view which shows the 1st form for implementing the metal halide discharge lamp of this invention Similarly enlarged plan view of arc tube The circuit block diagram of one form for implementing the metal halide discharge lamp lighting device of the present invention BRIEF DESCRIPTION OF THE DRAWINGS FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Airtight container, 1a ... Enclosing part, 1b ... Sealing part, 1c ... Discharge space, 2A ... Anode, 2K ... Cathode, 3A ... Sealing metal foil on the anode side, 3B ... Sealing metal foil on the cathode side, 4A 4b: current introduction conductor, A1: anode main part, A2: shaft part, IT ... arc tube, K1 ... cathode main part, K2 ... shaft part, L _A : length of sealing metal foil on the anode side, L _K ... the length of the sealing metal foil on the cathode side

Claims (7)

A fire-resistant and light-transmitting hermetic container including a surrounding part in which a discharge space is formed and a pair of sealing parts that are connected to the surrounding part and in which a sealing metal foil is hermetically embedded;
Each base end is connected to a sealing metal foil embedded in the sealing part of the hermetic container, the electrode main part at the distal end is desired to be opposed to and separated from the surrounding part, and the middle part is supported by the sealing part, and the hermetic container An anode and a cathode sealed within;
A pair of current introduction conductors whose front ends are connected to a sealing metal foil embedded in the pair of sealing portions and whose other ends are exposed to the outside from the sealing portions;
The first halide, the second halide, and a rare gas are enclosed in an airtight container, and the first halide is selected from the group consisting of sodium (Na), scandium (Sc), and a rare earth metal. One or a plurality of halides, the second halide being magnesium (Mg), iron (Fe), cobalt (Co), chromium (Cr), zinc (Zn), nickel (Ni), manganese ( Mn), aluminum (Al), antimony (Sb), beryllium (Be), rhenium (Re), gallium (Ga), titanium (Ti), zirconium (Zr), hafnium (Hf), tin (Sn) and indium ( A discharge medium that is essentially free of mercury and is a halide of one or more metals selected from the group consisting of In) ;
The direction of the current flowing in the hermetic container is a single direction that does not change with time, and the length of the anode-side sealed metal foil is larger than the length of the cathode-side sealed metal foil, and A metal halide discharge lamp having a length of 10 to 19 mm. The sealing metal foil embedded in the sealing part has a formula: 7.36 <L _A · when the length on the anode side is L _A (mm) and the lamp current during steady lighting is Q (A). 2. The metal halide discharge lamp according to claim 1, wherein Q <15.12 is satisfied.   3. A metal halide discharge lamp according to claim 1, wherein a base is disposed in the anode-side sealing portion.   4. The metal halide discharge lamp according to claim 1, wherein the rare gas of the discharge medium is sealed at 1 atm or more.   5. The metal halide discharge lamp according to claim 1, wherein the rated lamp power is 35 W. A metal halide discharge lamp according to any one of claims 1 to 5;
A DC electronic lighting circuit that supplies a metal halide discharge lamp with a current whose polarity does not change with time;
A metal halide discharge lamp lighting device comprising: A lighting device body;
A metal halide discharge lamp lighting device according to claim 6 disposed in the lighting device body;
An illumination device comprising:

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