JP2005093356A - Metal halide lamp and lighting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal halide lamp improved in a luminous flux maintenance rate by restraining an airtight vessel from being blackened by dispersal of an electrode substance by regulating sizes of the airtight vessel and an electrode without any additional structure; and to provide a lighting system using it. <P>SOLUTION: This metal halide lamp consists of: the fire-resistant and translucent airtight vessel 1 having an inside volume ≤0.05 cc and having a surrounding part 1a with a length L of 6.5±0.2 mm; a pair of electrodes 1b, 1b enclosed in the airtight vessel 1 by facing to each other at an inter-electrode distance of 4.2±0.3 mm and each having a shaft diameter of 0.3-0.4 mm; and a discharge medium containing a metal halide containing a luminescent metal and Xe of 5 atmospheres at 25°C and enclosed in the airtight vessel 1 without substantially containing mercury. The tube wall load thereof is ≥50 W/cm<SP>2</SP>in a stable time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a metal halide lamp that does not enclose mercury and an illumination device using the same.

A metal halide lamp for automobile headlamps that does not enclose mercury with a large environmental load is known (for example, see Patent Document 1). Patent Document 1 discloses a ScI ₃ —NaI—InI ₃ sealed lamp in which InI ₃ or the like is sealed instead of mercury. Thereby, it has a favorable start characteristic and the electrical characteristic and light emission characteristic substantially equivalent to the metal halide lamp containing mercury are acquired.

  Although metal halide lamps that do not contain mercury have almost the same electrical characteristics as mercury-containing metal halide lamps as described above, they are not exactly the same, and the lamp voltage tends to be lower than that of mercury-containing metal halide lamps. Therefore, when the same level of lamp power is applied, the value of the lamp current becomes considerably large. For this reason, the temperature of the electrode becomes excessive, and the problem of blackening caused by the scattering of the electrode material becomes so great that it cannot be compared.

  Then, when the electrode material is scattered and the inner surface of the arc tube is blackened, the luminous flux maintenance factor is lowered. In a small metal halide lamp having an inner volume of 0.05 cc or less, the inner surface area of the hermetic container is small. Therefore, when blackening occurs due to scattering of the electrode material, the influence on the total luminous flux is increased.

On the other hand, it is known that the electrode shaft of a metal halide lamp for an automobile headlamp is covered with a metal body having a predetermined weight to prevent blackening of the inner surface of the arc tube and prevent an early decrease in the luminous flux maintenance factor. (See Patent Document 2). In Patent Document 2, a metal body is covered by winding a tungsten wire around an electrode in a coil shape.
JP 11-238488 A JP-A-12-268773

  However, in the configuration as in Patent Document 2, since a metal body is added and a process for covering the periphery of the electrode with the metal body is required, the structure becomes complicated and the manufacturing becomes troublesome. There is a problem of inviting. On the other hand, it is possible to suppress blackening by controlling the shape of the electrode. However, if the electrode shape is changed, flickering of brightness tends to occur.

  The present invention relates to a metal halide lamp that improves the luminous flux maintenance factor by suppressing the blackening of the hermetic container due to scattering of the electrode material by regulating the dimensions of the hermetic container and the electrode without an additional structure, and an illumination device using the same The purpose is to provide.

The metal halide lamp according to the first aspect of the present invention is a fire-resistant and light-transmitting hermetic container having an inner volume of 0.05 cc or less and a length of the surrounding portion of 6.5 ± 0.2 mm; A pair of electrodes facing each other with an electrode distance of 2 ± 0.3 mm and an axial diameter of 0.3 to 0.4 mm; a metal halide containing a luminescent metal, and at least 5 atm at 25 ° C. A discharge medium containing Xe and enclosed in an airtight container and essentially free of mercury, and having a tube wall load of 50 W / cm ² or more when stable.

  In the present invention and each of the following inventions, the definitions and technical meanings of terms are as follows unless otherwise specified.

  <Regarding the Airtight Container> The airtight container is fireproof and translucent. “Fire resistance” means sufficiently withstanding the normal operating temperature of the discharge lamp. Therefore, the hermetic container may be made of any material as long as it is a material having fire resistance and visible light in a desired wavelength region generated by discharge can be derived to the outside. For example, it can be formed using quartz glass, translucent alumina, polycrystalline ceramics such as YAG, or single crystals thereof. However, in the case of an automotive headlamp, a high light collection efficiency is required, so that quartz glass having a high linear transmittance is suitable. If necessary, it is allowed to form a halogen-resistant or halogenated-resistant transparent coating on the inner surface of the quartz glass hermetic container or to modify the inner surface of the hermetic container.

  Moreover, the airtight container has a discharge space with an internal volume of 0.05 cc or less formed therein. The discharge space preferably has a substantially cylindrical shape with an inner diameter of 2.3 to 2.7 mm, and has an elongated shape having a length of 6.0 to 7.7 mm in the axial direction. As a result, the arc tends to bend upward in the horizontal lighting, and therefore approaches the upper inner surface of the hermetic container, so that the temperature rise at the upper part of the hermetic container is accelerated.

  Further, the airtight container has a length in the tube axis direction of the surrounding portion defined as 6.5 ± 0.2 mm. This length is effective for making the protrusion length with respect to the inside of the surrounding portion of the electrode suitable for suppressing the scattering of the electrode material from the electrode tip while maintaining the distance between the electrodes at 5 mm. is there.

  In addition, the thickness of the part surrounding the discharge space of the surrounding part can be made relatively large. That is, the thickness at the substantially central portion of the distance between the electrodes can be made larger than the thickness at both sides. As a result, the heat transfer of the hermetic container is improved and the temperature rise of the discharge medium adhering to the lower part of the discharge space and the inner side surface of the hermetic container is accelerated, so that the rise of the luminous flux is accelerated. The “length in the tube axis direction of the surrounding portion” means a discontinuous portion formed between the surrounding portion and a pair of sealing portions as described later extending from both ends thereof, for example, a pair of reduced diameters. The distance between the parts. In addition, when there is no clear discontinuity at both ends of the surrounding portion, a value obtained by adding 2.3 mm to the distance between the electrodes is referred to as the length of the surrounding portion in the tube axis direction.

  Furthermore, in order to seal the electrode described later in the hermetic container, a pair of sealing portions in the form of rods are integrally formed at both ends in the axial direction of the discharge space formed inside the hermetic container. Can do. Then, the electrode and the external lead wire are connected through a sealing metal foil embedded in the pair of sealed portions, preferably by the reduced pressure sealing method or by the combined use of the reduced pressure sealing method and the pinch sealing method. Thus, current can be supplied to the electrodes, and the surrounding portion can be made chipless so that the light distribution characteristics can be prevented from being disturbed by the exhaust tip portion.

  <About a pair of electrodes> A pair of electrodes are made of a high melting point metal, have an axial diameter of 0.3 to 0.4 mm, and are sealed in an airtight container so that the distance between the electrodes is 5 mm or less. Has been. The refractory metal can be composed of tungsten, doped tungsten, rhenium, rhenium-tungsten alloy, or the like. Further, as a structure in which the electrode is sealed in the hermetic container, the base end portion of the electrode can be embedded and supported in a pair of sealing portions of the hermetic container. Note that the base end of the electrode is connected to a sealing metal foil made of molybdenum or the like embedded in a hermetically sealed portion by means such as welding.

  Further, the electrode reaches the tip without increasing its diameter from the shaft portion, and the tip has a flat end surface, or the tip from which the arc starts forms a curved surface. Alternatively, a portion larger in diameter than the shaft portion can be formed at the tip of the shaft portion. Note that when a curved surface is formed at the tip that becomes the starting point of the arc without reaching a diameter from the shaft portion of the electrode, the curved surface is a curved surface that constitutes a part of a substantially spherical shape. By setting the radius to ½ or less of the diameter of the shaft portion, undesired movement of the starting point of the arc can be suppressed, and the occurrence of brightness flickering can be reduced. The “tip that is the starting point of the arc of the electrode” means a portion that is the starting point of the arc on the tip side of the electrode, and does not necessarily indicate the entire geometric tip of the electrode. That is, it is only necessary to form a curved surface on the tip end side of the electrode and having a radius of 1/2 or less with respect to the diameter of the shaft portion of the electrode at the site where the arc starts. However, the curved surface at the tip that is the starting point of the arc of the electrode preferably has a radius of 40% or more of ½ of the diameter of the shaft portion.

  Furthermore, the length of the electrode protruding into the hermetic vessel affects the electrode temperature as well as the shaft diameter. However, it is only necessary to follow the usual practice of this type of small metal halide lamp, and the electrode can be either AC or DC. It may be configured to operate. When operating with alternating current, the pair of electrodes have the same structure. When operating with direct current, the temperature of the anode generally increases greatly, so that the shaft diameter can be made larger than that of the cathode to increase the heat radiation area, and frequent flashing can be accommodated.

  Furthermore, as a structure in which the electrode is sealed in the hermetic container, the base end portion of the electrode can be embedded and supported in a pair of sealing portions of the hermetic container. Note that the base end of the electrode is connected to a sealing metal foil made of molybdenum or the like embedded in a hermetically sealed portion by means such as welding.

  <Discharge Medium> The discharge medium contains a metal halide and Xe of 5 atm or more at 25 ° C. and essentially does not contain mercury. The specific name of the metal halide is not particularly limited, but preferably includes a halide of Sc and a halide of at least one metal selected from the group of Na and rare earth metals. . The above metal is a main light emitting metal that efficiently emits white light. In the case of the metal halide, a halide of another metal can be selected and added as an auxiliary light-emitting metal as desired.

In addition, when the above-mentioned luminescent metal halide is used as the first metal halide, in order to increase the lamp voltage mainly to a desired level in addition to the first metal halide, the second metal halide is used. Can be encapsulated. The second metal halide is preferably composed of a halide of Zn and / or a halide of In. Since these metals have a sufficiently high vapor pressure, they are effective as a lamp voltage forming medium instead of mercury. However, since these metals emit blue light at the same time, they also have the effect of correcting the chromaticity of white light emission of the main light-emitting substance constituting the first metal halide. Incidentally, specific examples halides an In, InI, the InI ₃ and InBr contemplated. Any of these may be used. In addition, ZnI ₂ can be used as a halide of Zn.

  In addition to the above metal as the second metal halide, or a metal halide selected from the following group alone can be encapsulated as a lamp voltage forming medium. That is, by encapsulating one or a plurality of metal halides selected from the group of Mg, Co, Cr, Mn, Sb, Re, Ga, Sn, Fe, Al, Ti, Zr and Hf, the lamp is mainly used. The voltage can be mainly formed. The above group of metals are not expected to be metals that have high vapor pressure and do not emit light in the visible range, or that emit relatively little light, that is, light emitting metals, but are mainly suitable for forming lamp voltage. is there.

  Thus, as a second halide, in addition to the above Zn and In, as an auxiliary lamp voltage forming medium, or in place of them, the above group metal halides can be used as in the present invention. In a small metal halide lamp, a lamp voltage of about 25 to 70 V can be obtained without using mercury. For this reason, it becomes possible to supply the required lamp power with a relatively small lamp current.

  Next, the halogen constituting the halide will be described. That is, iodine is most suitable for the reactivity, and at least the main light emitting metal is mainly enclosed as iodide. However, if necessary, different halogen compounds such as iodide and bromide can be used in combination.

  Xe of 5 atm or more acts as a starting gas and a buffer gas, and can contribute white light emission of Xe as a luminous flux at the time of rising when the vapor pressure of the luminescent metal immediately after lighting is low. Xe is preferably sealed in a range of 8 to 16 atmospheres as a metal halide lamp for an automobile headlamp.

In addition, mention mercury. In the present invention, “essentially free of mercury” means that not only mercury is not enclosed, but there is less than 2 mg, preferably 1 mg or less of mercury per 1 cc of internal volume of the airtight container. It means to allow. However, it is environmentally desirable not to enclose mercury at all. When the lamp voltage of the discharge lamp is increased to a required level with mercury vapor as in the conventional case, the short arc type may contain 20 to 40 mg per 1 cm ³ of the inner volume of the hermetic container, and moreover 50 mg or more in some cases. It can be said that the amount of mercury is substantially low.

<Regarding the tube wall load> The tube wall load refers to the lamp power per 1 cm ² of the unit inner surface area of the hermetic container, and is 50 W / cm ² or more in the present invention. For example, when a metal halide lamp for an automobile headlamp is operated under a high tube wall load as described above in order to accelerate the rise of the luminous flux immediately after lighting, the black on the inner surface of the hermetic container due to the scattering of the electrode material. Therefore, the benefits of the present invention can be enjoyed.

  <Regarding the Action of the Present Invention> The present invention has the above-described configuration, so that the period when the power supplied to the lamp immediately after lighting is 2.5 times or more of that at the stable time is 2 seconds or longer, for example, about 4 seconds. It was discovered that even when the light is lit with a high tube wall load, such as when lit under the above conditions, the scattering of the electrode material is suppressed, and therefore the blackening of the inner surface of the hermetic container is reduced. For this reason, the fall of the luminous flux maintenance factor during a lifetime was suppressed. This is presumably because the tip end temperature of the pair of electrodes is moderately reduced by defining the length of the enclosure portion of the hermetic container as described above.

  Further, since it is not necessary to change the electrode shape in order to suppress scattering of the electrode material, no flickering of brightness occurs.

  <Other Configurations of the Present Invention> In the present invention, although not an essential configuration requirement, the performance of the metal halide lamp is improved or the function is increased by selectively adding the following configurations.

  1. (Outer tube) The outer tube contains an airtight container. The outer tube shields the ultraviolet rays radiated from the airtight container to the outside, keeps the airtight container warm, protects it mechanically, and arranges a light shielding film with a predetermined shape to adjust the light distribution characteristics as required. When it is provided, a light shielding film can be formed on the surface of the outer tube. Further, the inside of the outer tube may be hermetically sealed with respect to the outside air according to the purpose, or air or an inert gas having the same or reduced pressure as the outside air may be enclosed. Further, if necessary, it may communicate with the outside air.

  2. (About the base) The base functions to connect the metal halide lamp to the lighting circuit and, in addition, to mechanically support the lamp.

  3. (Regarding the igniter) The igniter is a means for generating a high voltage pulse voltage and applying it to the metal halide lamp to promote its start-up. It can also be integrated with the metal halide lamp by storing it inside the base. it can.

  4). (Starting auxiliary conductor) The starting auxiliary conductor is a means for increasing the electric field strength in the vicinity of the electrode to assist the start of the metal halide lamp. If necessary, one end is connected to the same potential as the other electrode, and the other end is connected. Is disposed on the outer surface of the discharge vessel in the vicinity of one of the electrodes.

    A lighting device according to a second aspect of the present invention comprises: a lighting device body; and the metal halide lamp according to claim 1 disposed in the lighting device body; and a lighting device for lighting the metal halide lamp. Yes.

  In the present invention, the “illumination device” is a broad concept including all devices using a metal halide lamp as a light source, such as an automobile headlamp, a lighting fixture, a signal light, a marker lamp, an optical fiber illumination device, a photochemical reaction device, and the like. is there. The “illuminating device main body” means all remaining portions excluding the metal halide lamp and the lighting circuit from the lighting device.

  The lighting circuit is means for lighting the metal halide lamp, and is preferably an electronic one. However, if necessary, the lighting circuit may be mainly composed of a coil and an iron core. In the case of a lighting circuit for an automobile headlamp, the maximum input power up to 4 seconds immediately after the lighting of the metal halide lamp is set to 2 to 4 times, preferably 2.5 to 4 times the lamp power when stable. Thus, the rise of the luminous flux can be accelerated so as to fall within a range required for an automobile headlamp. Note that when the enclosure pressure of Xe as a rare gas is X (atmospheric pressure) in the range of 5 to 15 atm, and the maximum input power up to 4 seconds immediately after the metal halide lamp is turned on is AA (W), AA is By satisfying the configuration, it is possible to obtain a luminous intensity of 8000 cd at a representative point on the front face of the headlamp necessary for an automotive headlamp by speeding up the rise of the light beam up to 4 seconds immediately after lighting.

AA> −2.5X + 102.5
As described above, since the Xe enclosed pressure and the maximum input power have a linear relationship only with a discharge medium having a low vapor pressure, the emission of xenon becomes overwhelming at the point of 4 seconds after starting. Because. The amount of light emitted from Xe is determined by the enclosed pressure of Xe and the power at that time. Therefore, if the Xe pressure is low, the input power may be increased. Conversely, if the Xe pressure is high, the input power may be reduced. In the present invention, the lighting of the metal halide lamp may be either AC lighting or DC lighting.
Further, the lighting circuit can be configured to have a no-load output voltage of 200 V or less as required. Since a metal halide lamp that does not enclose mercury generally has a lower lamp voltage than a metal halide lamp containing mercury, the no-load output voltage of the lighting circuit can be reduced to 200 V or less. As a result, the lighting circuit can be miniaturized. Note that a mercury-containing metal halide lamp requires a no-load output voltage of about 400V.

    According to the invention of claim 1, the inner volume of the airtight container is 0.05 cc or less, the length of the surrounding portion is 6.5 ± 0.2 mm, and the shaft diameter of the pair of electrodes is 0.3 to 0.4 mm. Thus, by providing the distance between the electrodes of 4.2 ± 0.3 mm, it is possible to provide a metal halide lamp that improves the luminous flux maintenance factor by suppressing blackening of the hermetic container due to scattering of the electrode material without an additional structure. Can do.

    According to invention of Claim 2, the illuminating device which has the effect of Claim 1 can be provided.

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

    1 and 2 show a metal halide lamp for an automobile headlamp as an embodiment of the metal halide lamp of the present invention, FIG. 1 is a front view, and FIG. 2 is an enlarged plan view of a main part. In each figure, IT is a discharge vessel or arc tube, 2, 2 is a pair of sealing metal foils, 3A and 3B are a pair of current introduction conductors, OT is an outer tube, T is an insulating tube, and B is a base.

  The discharge vessel IT includes an airtight vessel 1 and a pair of electrodes 1b and 1b. The airtight container 1 includes an enclosing portion 1a formed into a hollow spindle shape, a pair of sealing portions 1a1, and a sealing tube 1a2. A pair of reduced diameter portions 1a3 and 1a3 are formed between the surrounding portion 1a and the pair of sealing portions 1a1 and 1a2. The distance between the pair of reduced diameter portions 1a3 and 1a3 represents the length L of the surrounding portion 1a in the tube axis direction. Moreover, the surrounding part 1a has the elongate substantially cylindrical discharge space 1c in the inside. The pair of left and right sealing portions 1a1 are elongated and extend in the tube axis direction from both ends of the surrounding portion 1a in the tube axis direction. The sealing tube 1a2 is integrally formed with the left sealing portion 1a1 in FIG. 1 and enters the base B.

  The pair of electrodes 1b and 1b are laser-welded to one end of a sealing metal foil 2 (described later) whose base ends are embedded in the sealing portion 1a1, and an intermediate portion is embedded in the sealing portion 1a1 and loosened. By being supported, it is disposed at a predetermined position, and the tip protrudes into the discharge space 1c so as to face and separate from both ends.

  The pair of sealing metal foils 2 and 2 are made of molybdenum foil, and are embedded in the sealing portion 1a1 of the airtight container 1 in an airtight manner.

  The pair of current introduction conductors 3A and 3B have their distal ends welded to the other end of the sealing metal foil 2 in the sealing portions 1a1 at both ends of the hermetic container 1, and their proximal ends led out to the outside of the sealing portion 1a1. Has been. In the drawing, the current introduction conductor 3B led out from the discharge vessel IT to the right is folded back along an outer tube OT described later, and further introduced into a later-described base B, so that one base terminal 5 is provided. Connected to. In FIG. 1, a current introduction conductor 3A led out to the left along the tube axis from the discharge vessel IT extends along the tube axis, is introduced into the base B, and is connected to the other base terminal (not shown). doing.

  In the hermetic vessel 1a, a discharge medium composed of first and second halides and Xe is enclosed as a discharge medium. The first halide consists of a halide of Sc and a halide of Na. The second halide is made of Zn halide.

  The outer tube OT has an ultraviolet ray cutting performance, and the discharge vessel IT is accommodated therein, and the reduced diameter portion 6 on the tip side is glass-welded at a position shown in the drawing of the sealing portion 1a1 of the discharge vessel IT. Yes. The other reduced diameter portion (not shown) is supported by glass welding to the sealing tube 1a2. However, the inside of the outer tube OT is not airtight but communicates with the outside air.

  The insulating tube T covers the current introduction conductor 3B.

  The base B is standardized for automobile headlamps, supports the discharge vessel IT and the outer tube OT along the central axis, and is detachable from the back of the automobile headlamp. It is configured to be mounted. The base B includes a support band 4 that protrudes from the front surface in the tube axis direction and that holds the base end portion of the outer tube OT.

  In the first embodiment shown in FIG. 1 and FIG.

Discharge vessel IT
Airtight container 1a: made of quartz glass, inner volume 0.03cc, maximum inner diameter of enclosure
2.7 mm, length of the surrounding portion in the tube axis direction is 6.5 mm, maximum outer diameter
6.0mm
Electrode: shaft diameter 0.4 mm, protrusion length 1.2 mm, operating temperature 1800 ° C.
Distance between electrodes: 4.2 mm
Discharge medium Metal halide: ScI ₃ —NaI—ZnI ₂ = 0.2 mg
Xe: 10 atm Outer tube OT: Outer diameter 9 mm, inner diameter 7 mm, internal atmosphere; atmospheric pressure (atmosphere)
Input power immediately after lighting: 80W
Input current immediately after lighting: 2.8A
Stable lamp voltage: 42V
Lamp current when stable: 0.8A
Lamp power when stable: 35W
[Comparative example]
Airtight container 1a: Length of the surrounding portion in the tube axis direction 6.5 mm
Electrode: Pure W, operating temperature 1800 ° C
Other: Same Specifications as Example 1 Next, the measurement results of the luminous flux maintenance factor of the above example will be described with reference to FIG.

    FIG. 3 is a graph showing the luminous flux maintenance factor in an example of a metal halide lamp for an automobile headlamp as one embodiment of the metal halide lamp of the present invention together with that in a comparative example. In the figure, the horizontal axis indicates the lighting time (H), and the vertical axis indicates the luminous flux maintenance factor (%). In the figure, curve A is an example and curve B is a comparative example.

  As can be seen from the figure, in the above-described embodiment of the present invention, the luminous flux maintenance factor is about 5% higher than the comparative example at 2000 hours of lighting, and the luminous flux maintenance factor is clearly superior.

    4 and 5 show an automobile headlamp device as an embodiment of the lighting device of the present invention, FIG. 4 is a perspective view seen from the back side, and FIG. 5 is a circuit diagram of a lighting circuit. In FIG. 4, the vehicle headlamp device HL is configured by a vehicle headlamp device body 21, a metal halide lamp HPDL, and two lighting circuits OC.

  The automotive headlamp device main body 21 includes a front transmission panel 21a, reflectors 21b and 21c, a lamp socket 21d, a mounting portion 21e, and the like. The front lens 21a has a shape combined with the outer surface of the automobile, and includes necessary optical means such as a prism. The reflectors 21b and 21c are provided for each metal halide lamp HPDL, and are configured to obtain light distribution characteristics required for each. The lamp socket 21d is connected to the output end of the lighting circuit OC and is attached to the base 21d of the metal halide lamp HPDL. The attachment portion 21e is a means for attaching the automobile headlamp device body 21 to a predetermined position of the automobile.

  The metal halide lamp HPDL has the structure shown in FIG. The lamp socket 21d is attached to and connected to the base. Thus, the two metal halide lamps KPDL are mounted on the vehicle headlight device main body 21 to constitute a four-lamp vehicle headlight device. The light emitting portion of each metal halide lamp HPDL is located substantially at the focal point of the reflectors 21b and 21c of the automotive headlamp device body 21.

  Each of the two lighting circuits OL has a circuit configuration to be described later, is housed in the metal container 22, and energizes and lights the metal halide lamp HPDL.

  As shown in FIG. 5, the lighting circuit OL includes a DC power source 11, a chopper 12, a control unit 13, a lamp current detection unit 14, a lamp voltage detection unit 15, an igniter 16, a metal halide lamp HPDL, and a full bridge inverter 17. Then, the metal halide lamp HPDL is lit in alternating current.

  The DC power source 11 is means for supplying DC power to a chopper 12 described later, and a battery or a rectified DC power source 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 11a is connected in parallel to perform smoothing.

  The chopper 12 is a DC-DC conversion circuit that converts a DC voltage into a DC voltage of a required value, and controls the metal halide lamp HPDL through a full bridge inverter 17 described later. 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 means 13 controls the chopper 12. For example, immediately after lighting, a metal halide lamp HPDL is supplied with a lamp current more than three times the rated lamp current from the chopper 22 via the full bridge inverter 17, and then the lamp current is gradually reduced over time. Control to make the lamp current. Further, the control means 13 generates a constant power control signal and performs constant power control of the chopper 22 by receiving feedback input of detection signals corresponding to the lamp current and the lamp voltage as will be described later. Further, the control means 13 has a built-in microcomputer in which a temporal control pattern is incorporated in advance, and immediately after the lamp is turned on, a lamp current more than three times the rated lamp current is supplied to the metal halide lamp HPDL. The chopper 12 is configured to control the current.

  The lamp current detection unit 14 is inserted in series with the lamp via the full bridge inverter 17, detects a current corresponding to the lamp current, and inputs the control input to the control unit 13.

  Similarly, the lamp voltage detection means 15 is connected in parallel with the metal halide lamp HPDL via the full bridge inverter 17, detects a voltage corresponding to the lamp voltage, and inputs the control input to the control means 23.

  The igniter 16 is interposed between the full bridge inverter 17 and the metal halide lamp HPDL, and is configured to supply a starting pulse voltage of about 20 kV to the metal halide lamp HPDL at the time of starting.

  The full bridge inverter 17 includes a bridge circuit composed of four MOSFETs Q1, Q2, Q3 and Q4, a MOSFET Q1 and Q3 of the bridge circuit 17a, a gate drive circuit 28b for alternately switching Q2 and Q4, and a polarity inversion circuit INV. Then, the DC voltage from the chopper 12 is converted into a rectangular-wave low-frequency AC voltage by the above switching and applied to the metal halide lamp HPDL to light the metal halide lamp HPDL with low-frequency AC lighting.

  Then, when the metal halide lamp HPDL is turned on with a rectangular wave low frequency alternating current using the lighting circuit OC, a required light flux is generated immediately after the 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.

The front view which shows the metal halide lamp for motor vehicle headlamps as one Embodiment in the metal halide lamp of this invention Similarly, the main part enlarged plan view The graph which shows the luminous flux maintenance factor in the Example of the metal halide lamp for motor vehicle headlamps as 1st Embodiment in the metal halide lamp of this invention with it in a comparative example The perspective view seen from the back direction which shows the automobile headlamp device as one embodiment of the lighting installation of the present invention Similarly, the circuit diagram of the lighting circuit

Explanation of symbols

      DESCRIPTION OF SYMBOLS 1 ... Airtight container, 1a ... Enclosing part, 1a1 ... Sealing part, 1a2 ... Sealing tube part, 1a32 ... Reduced diameter part, 1c ... Discharge space, 2 ... Sealing metal foil, 1b ... Electrode, 3A ... Current introduction conductor 3B: current introduction conductor, B: base, IT ... discharge vessel, OT ... outer tube, T ... insulating tube

Claims (2)

A fire-resistant and translucent airtight container having an internal volume of 0.05 cc or less and a length of the surrounding portion of 6.5 ± 0.2 mm;
A pair of electrodes sealed opposite to each other with a distance between electrodes of 4.2 ± 0.3 mm and having an axial diameter of 0.3 to 0.4 mm;
A discharge medium containing a metal halide containing a luminescent metal and Xe at 5 atm or more at 25 ° C. and enclosed in an airtight container and essentially free of mercury;
And a metal halide lamp characterized by having a tube wall load of 50 W / cm ² or more when stable. A lighting device body;
The metal halide lamp according to claim 1, wherein the metal halide lamp is disposed in a lighting device body;
A lighting device for lighting a metal halide lamp;
An illumination device comprising:

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