JP2008098045A - Metal halide lamp for automobile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal halide lamp for an automobile which has quick start-up of flux of light while suppressing leakage from an axis and wear of electrodes. <P>SOLUTION: The metal halide lamp for the automobile is equipped with an airtight container 1 having a discharge portion 11 with a discharge space 14 formed inside and sealing portions 12a, 12b formed at both ends of the discharge portion 11, a discharge medium which is filled in a discharge space 14 and contains a metal halide 2 and rare gas, but does not contain mercury in substance, and a pair of electrodes of which base end side is installed in sealing parts 12a, 12b and top end side is arranged opposed to each other in the discharge space 14. The metal halide 2 contains at least halogenated indium and the mole number of the halogenated indium is 2.0×10<SP>-7</SP>or more, the diameter R of the electrodes 3a2, 3b2 installed in the sealing portions 12a, 12b is 0.32 mm or more and 0.38 mm or less, and electric power of two times or more of the power at a steady state is supplied at the time of start, and the lamp is lighted. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an automotive metal halide lamp which is essentially free of mercury and is used in automotive headlamps.

  A metal halide lamp that does not contain mercury (hereinafter referred to as a mercury-free lamp) is known, for example, from Japanese Patent Laid-Open No. 2001-6610 (Patent Document 1). Mercury-free lamps can obtain characteristics equivalent to or better than mercury-containing metal halide lamps (hereinafter, mercury-containing lamps) by combining metal halides and rare gases. In Patent Document 1, a lamp is composed of sodium halide, scandium halide, indium halide, and xenon.

JP 2001-6610 A

  When a metal halide lamp is used as a headlight of an automobile, it is required that the brightness of the lamp can be obtained quickly immediately after lighting in consideration of safety, that is, that the so-called luminous flux rises quickly. However, since the mercury-free lamp does not enclose mercury, it is difficult to obtain light emission immediately after starting. Therefore, when attention was paid to the indium halide described in Patent Document 1 that the rise time of the light beam can be shortened, the test was performed. It was found that a mercury-free lamp that tends to be early can be created.

  However, in such a mercury-free lamp that has accelerated the rise of the luminous flux, a phenomenon in which a so-called axial leak occurs, in which a crack occurs in the electrode portion sealed in the sealing portion, leading to a leak, or the electrode is significantly consumed. It was observed.

  As a result of investigations by the inventors on this problem, it has been found that when trying to accelerate the rise of the luminous flux in a mercury-free lamp, it must be combined with a suitably designed electrode. Therefore, as a result of further tests focusing on the electrodes, the present inventors have proposed the present invention because they have found a condition that can speed up the luminous flux rise while suppressing axial leakage and electrode wear.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a metal halide lamp for automobiles that has a quick rise in luminous flux while suppressing axial leakage and electrode wear.

In order to achieve the above object, an automotive metal halide lamp according to the present invention includes an airtight container having a discharge portion in which a discharge space is formed, sealing portions formed at both ends of the discharge portion, and the discharge space. A discharge medium containing a metal halide and a rare gas and essentially free of mercury, and a proximal end side sealed in the sealing portion and a distal end side disposed opposite to each other in the discharge space. A pair of electrodes, wherein the metal halide contains at least indium halide, and the indium halide has a mol number of 2.0 × 10 ⁻⁷ or more and is sealed in the sealing portion. The diameter R is not less than 0.32 mm and not more than 0.38 mm, and is characterized in that at the time of start-up, power more than twice the power at the time of stabilization is supplied.

  ADVANTAGE OF THE INVENTION According to this invention, the metal halide lamp for motor vehicles with quick light beam rise can be provided, suppressing axial leak and consumption of an electrode.

(First embodiment)
Hereinafter, an automotive metal halide lamp according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall view for explaining a first embodiment of a metal halide lamp for an automobile of the present invention.

  The metal halide lamp for automobiles has an airtight container 1 as a discharge container. The hermetic container 1 can be made of, for example, quartz glass, but any material that has excellent heat resistance and translucency can be used. The hermetic container 1 has an elongated shape in the lamp axis direction, and a substantially elliptical discharge portion 11 is formed at a substantially central portion thereof. Plate-shaped sealing portions 12a and 12b are formed at both ends of the discharge portion 11, and cylindrical non-sealing portions 13a and 13b are formed at both ends thereof.

  Inside the discharge part 11, a discharge space 14 having a substantially cylindrical shape at the center and tapered at both ends is formed in the axial direction. It is desirable that the volume of the discharge space 14 is 0.01 cc to 0.04 cc when the application is specified for a vehicle headlamp.

  The discharge space 14 is filled with a discharge medium composed of the metal halide 2 and a rare gas.

The metal halide 2 is composed of scandium halide, sodium halide, or indium halide. Specifically, scandium iodide (ScI ₃ ), sodium iodide (NaI), and indium bromide (InBr). In addition, zinc halide and tin halide can be added. Moreover, as halogen couple | bonded with these metals, the halogen of iodine, bromine, and chlorine can also be used 1 type or in combination.

  As the rare gas, xenon which has high luminous efficiency immediately after starting and mainly acts as a starting gas is enclosed. Note that the pressure of the rare gas desirably affects the rise of the luminous flux, and is preferably 8 to 18 atm at room temperature (25 ° C.). In addition to xenon, neon, argon, krypton, or the like may be used, or a combination thereof may be used.

  Here, the discharge space 14 essentially does not contain mercury. This “essentially mercury-free” means that it contains no mercury at all, or an amount equivalent to that which is hardly enclosed even when compared with a conventional mercury-containing discharge lamp, for example, less than 2 mg per ml, preferably Shall be allowed even in the presence of mercury of 1 mg or less.

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, coils 3a3 and 3b3, and external lead wires 3a4 and 3b4.

  Metal foil 3a1, 3b1, for example, a thin metal plate made of molybdenum.

  The electrodes 3a2, 3b2 are straight rods and are made of a material mainly composed of tungsten, for example, a material obtained by doping tungsten with thorium oxide. The front ends thereof are opposed to each other while maintaining a predetermined inter-electrode distance in the discharge space 14. Here, the “predetermined interelectrode distance” is preferably 5 mm or less for a short arc lamp, and further about 4.2 mm when used for an automobile headlamp.

  On the other hand, the base end side is connected to the end of the metal foils 3a1, 3b1 on the discharge part 11 side by welding. That is, the electrode portions from the joint portions with the metal foils 3a1 and 3b1 to the discharge space 14 are sealed with the quartz glass of the sealing portions 12a and 12b.

  The coils 3a3 and 3b3 are made of, for example, doped tungsten, and are spirally wound around the electrodes 3a2 and 3b2 from the end portions of the metal foils 3a1 and 3b1 toward the discharge space 14.

  The external lead wires 3a4 and 3b4 are made of, for example, molybdenum, and are connected to end portions of the metal foils 3a1 and 3b1 on the opposite side to the discharge portion 11 by welding or the like. The other end sides of the external lead wires 3a4 and 3b4 extend to the outside of the sealing portions 12a and 12b along the tube axis. Note that one end of an L-shaped support wire 3c made of nickel is connected to the lead wire 3b4 on the front end side extending to the outside, and the other end extends in the direction of a socket 6 described later. The portion of the support wire 3c parallel to the tube axis is covered with an insulating sleeve 4 made of ceramic.

  A cylindrical outer tube 5 having an action of blocking ultraviolet rays by adding an oxide such as titanium, cerium, or aluminum to quartz glass is provided outside the hermetic container 1 configured as described above along the tube axis. The airtight container 1 is provided substantially concentrically. These connections are made by melting the cylindrical non-sealing portions 13a, 13b at both ends of the hermetic container 1 and both ends of the outer tube 5. The space formed by the hermetic container 1 and the outer tube 5 can be filled with a rare gas such as nitrogen, neon, argon, or xenon, for example, or a mixture thereof.

  A socket 6 is connected to the non-sealed portion 13a side of the outer tube 5 in a state where the hermetic container 1 is covered inside. The metal band 71 attached to the outer peripheral surface of the outer tube 5 in the vicinity of the non-sealing portion 13a is connected to the four metal tongue pieces formed on the opening end of the socket 6 on the airtight container 1 holding side. 72 (two are shown in FIG. 1). And in order to strengthen a connection further, the contact point of the metal band 71 and the tongue piece 72 is welded. A bottom terminal 8a is formed at the bottom of the socket 6 and is connected to the lead wire 3a4. A bottom terminal 8b is formed on the side of the socket 6 and is connected to the support wire 3c.

  The metal halide lamp for automobiles configured as described above is arranged with the tube axis in a substantially horizontal state, and a lighting circuit (not shown) is electrically connected to the bottom terminal 8a and the side terminal 8b. Is supplied with more than twice as much power and is lit. For example, as shown in FIG. 2, the light is turned on with a power of about 75 W at the start time and about 35 W at the stable time. It should be noted that at the time of start-up, immediately after power is supplied to the lamp, and at the time of stability, when a sufficient amount of time has passed since the start-up and the lamp power does not fluctuate, for example, one minute after the start.

  Based on FIG. 3, one specification of the metal halide lamp for automobiles of the present invention will be described.

Discharge vessel 1: quartz glass, discharge space 14 volume = 0.028 cc, inner diameter A = 2.5 mm, outer diameter B = 6.2 mm, longitudinal sphere length C = 7.8 mm,
Metal halide 2: ScI ₃ -NaI-InBr = 1: 0.364: 0.506, total encapsulation amount = 0.35 mg
Noble gas: xenon = 10 atm,
Mercury: 0 mg,
Metal foils 3a1, 3b1: made of molybdenum,
Electrodes 3a2, 3b2: made of triated tungsten, diameter R = 0.35 mm, distance between electrodes D = 4.4 mm,
Coils 3a3, 3b3: made of doped tungsten, coil pitch = 250%
External lead wires 3a4, 3b4: made of molybdenum, diameter = 0.6 mm,
Lighting conditions: 75W (2.8A) immediately after lighting, 35W (0.7A) when stable
In the above specifications, the lamp characteristics are realized such that the total luminous flux is 2600 lm, the luminous flux rising rate after 4 seconds is 80%, and the color temperature is 5500K. Note that the various tests shown below are performed based on this specification unless otherwise specified.

  FIG. 4 is a diagram showing the luminous flux rising rate after 4 seconds when the number of moles containing indium halide is changed.

As can be seen from the results, the rise time of the light flux varies depending on the number of moles of indium halide contained, and the rise ratio of the light flux after 4 seconds increases as the number of moles of indium halide contained increases. It can be seen that when the number of moles of indium halide contained is 2.0 × 10 ⁻⁷ or more, a lamp with a fast luminous flux rise can be realized.

  Here, even if the diameters R of the electrodes 3a2, 3b2 sealed in the sealing portions 12a, 12b were changed, the same results as in FIG. 3 were obtained. However, depending on the diameter R, it has been confirmed that the lamp is likely to be unlit frequently during its lifetime. Such lamp non-lighting hardly occurs in a lamp with a small amount of indium enclosed, and is therefore considered to be a particularly common problem when a large amount of indium is enclosed.

  FIG. 5 is a diagram showing the lamp remaining rate when the electrode diameter R is changed. The lamp remaining rate is the ratio of the number of lamps that have been lit to the number of lamps tested (n = 6). The lighting condition is a blinking cycle of a rated life test mode (EU mode) defined by JEL, which is a standard for an automotive headlamp HID light source.

  As can be seen from the results, when the electrode diameter R is 0.32 to 0.38 mm, there is no lamp that is unlit during 1000 hours of lighting, but at R = 0.30 mm and 0.40 mm, as the lighting time passes. The lamp remaining rate gradually decreases.

  The cause of non-lighting is mainly due to axial leak at R = 0.30 mm, and axial leak and extinction at R = 0.40 mm. The axial leak is considered to be related to the electrode temperature during lighting, but the details are unknown. On the other hand, the extinction that occurs at R = 0.40 mm is caused by the consumption of the electrode, and the consumption of the electrode is related to the starting point of an arc (hereinafter referred to as an arc spot) formed at the tip of the electrode.

  When the arc spot formation time of each lamp used in the test of FIG. 5 is measured by observing the state of the arc through the neutral density filter, the arc spot formation time is obtained when the diameter R is 0.30 to 0.38 mm. Was about 10 seconds, but when the diameter R was 0.40 mm, it was about 40 seconds. In an automobile metal halide lamp, when an arc spot is formed on an electrode, the discharge is stabilized and the temperature of the electrode is lowered. On the other hand, until the arc spot is formed on the electrode, it is called a diffusion mode, and the electrode is maintained at a high temperature. That is, if the time during which the arc spot is formed is slow, a large burden is placed on the electrode, and the tip of the electrode is particularly worn out. When the tip of the electrode is consumed, the lamp voltage increases or flickers occur. Therefore, it is considered that the extinction occurred at R = 0.40 mm. It should be noted that the arc spot formation time and the luminous flux rise are almost irrelevant, and the fact that the arc spot formation time is slow does not mean that the luminous flux rise is slow.

  For the above reasons, in order to realize a metal halide lamp for automobiles that is unlikely to be unlit in a lamp having a fast rise in luminous flux, the electrode diameter R must be 0.32 mm or more and 0.38 mm or less.

  In order to suppress the axial leak, it is effective to wind the coils 3a3 and 3b3 around the electrodes 3a2 and 3b2 sealed to the sealing portions 12a and 12b. This is because when the coils 3a3 and 3b3 are wound around the electrodes 3a2 and 3b2, it is possible to reduce the rate of occurrence of axial leakage. At that time, the luminous flux rise time does not substantially change. The design of the coils 3a3 and 3b3 is effective when the coil pitch is 100 to 600%, the coil diameter is 30 to 90 μm, and the winding length is 2.0 mm to 4.0 mm in the direction of the discharge space 14 from the foil end. It is.

  Here, when more practical characteristics are required for the metal halide lamp of the present embodiment, the total enclosed amount of the metal halide should be set to a suitable amount.

  FIG. 6 is a diagram showing a change in lamp voltage when the total amount of metal halide enclosed is changed.

  As can be seen from the figure, the larger the amount of metal halide enclosed, the higher the initial lamp voltage. Further, the lamp voltage tends to increase as the lighting time elapses. When the lamp voltage increases, the lamp current value decreases, so that the lamp flickers from a certain point in time, and in the worst case, the extinction phenomenon occurs and the lamp may be extinguished. In fact, flickering occurs when the amount of metal halide contained is 0.5 mg or 0.55 mg. Further, 0.5 mg disappears in one of the six, and 0.55 mg reduces to three in six. The phenomenon of disappearance was observed. On the other hand, those phenomena were not confirmed when the amount of metal halide enclosed was 0.40 mg. Therefore, it is desirable that the amount of metal halide enclosed be 0.40 mg or less (however, considering the decrease in the luminous flux maintenance factor during the lifetime), the amount is 0.10 mg or more.

Therefore, in this embodiment, indium halide contains 2.0 × 10 ⁻⁷ or more in moles, and the diameters R of the electrodes 3a2 and 3b2 sealed in the sealing portions 12a and 12b are 0.32 mm or more, 0 .38 mm or less, and lighting at about 75 W at start-up and about 35 W at the time of start-up makes it possible to speed up the light beam rise while suppressing axial leakage and electrode wear.

  Further, by winding the coils 3a3 and 3b3 around the electrodes 3a2 and 3b2 sealed by the sealing portions 12a and 12b, the occurrence of axial leakage can be further suppressed.

  Furthermore, since the metal halide 2 has a total enclosed amount of 0.4 mg or less, the lamp voltage during the lifetime can be kept low, and the occurrence of flickering and extinction can be suppressed.

The whole figure for demonstrating 1st Embodiment of the metal halide lamp for motor vehicles of this invention. The figure for demonstrating the input example of lamp electric power. The figure for demonstrating one specification of the metal halide lamp for motor vehicles. The figure for demonstrating the luminous flux rise rate after 4 second when changing the number of moles containing indium halide. The figure for demonstrating the lamp residual ratio by the difference in an electrode diameter. The figure for demonstrating the change of a lamp voltage when changing the total enclosure amount of a metal halide.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Airtight container 11 Discharge part 12a, 12b Sealing part 13a, 13b Unsealed part 14 Discharge space 2 Metal halide 2a, 2b Mount 3a1, 3b1 Metal foil 3a2, 3b2 Electrode 3a3, 3b3 Coil 3a4, 3b4 External lead wire 3c Support wire 4 Insulating tube 5 Outer tube 6 Socket 71 Metal band 72 Tongue piece 8a Bottom terminal 8b Side terminal

Claims (3)

An airtight container having a discharge part in which a discharge space is formed, a sealing part formed at both ends of the discharge part, and a metal halide and a rare gas sealed in the discharge space, mercury is essentially A discharge medium that is not included, and a base end side is sealed in the sealing portion, and a tip end side is provided with a pair of electrodes arranged to face each other in the discharge space,
The metal halide contains at least indium halide, the indium halide contains 2.0 × 10 ⁻⁷ or more in mole, and the diameter R of the electrode sealed in the sealing portion is 0.32 mm or more, 0.38 mm or less,
A metal halide lamp for automobiles, wherein at least two times more power than stable power is supplied at start-up.   The automobile metal halide lamp according to claim 1, wherein a coil is wound around the electrode sealed in the sealing portion.   The metal halide lamp for an automobile according to claim 1 or 2, wherein the metal halide has a total enclosed amount of 0.4 mg or less.

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