JP2005259428A - Metal halide lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain high luminous flux maintenance factor even while a discharge medium contains essentially no mercury. <P>SOLUTION: A pair of electrodes 21, 22 is faced on the inside of a discharge space 111 of a translucent sealed container 1 having a light emitting tube part 11 forming the discharge space 111 of 0.1 cc or less on the inside. A discharge medium containing a metal halide containing at least 90-150 μmol/cc sodium halide sealed in the light emitting tube part 11 and rare gas is sealed. The metal halide lamp constituted like this is lit at a tube wall load of 50 (W/cm<SP>2</SP>) or more. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a metal halide lamp used for an automobile headlamp or the like.

  In a conventional metal halide lamp, a pair of electrodes are opposed to a discharge space formed inside a light-transmitting hermetic vessel, and the discharge space contains a discharge medium containing sodium or scandium halide, a rare gas, or the like. Is enclosed. (For example, refer to Patent Document 1).

JP 2001-31998 A

  In the metal halide lamp as described in the above-mentioned Patent Document 1, sodium and scandium light-emitting metals that close most of the light emission of the lamp are enclosed in the lamp in the form of halide, and from the state of the metal halide by the heat of arc discharge. Although they emit light when they are dissociated, it is known that the vaporized sodium permeates through quartz glass, which is the material of the hermetic container, and the luminous flux maintenance factor is lowered by the amount of the transmitted sodium. Here, the luminous flux maintenance factor indicates the ratio of the luminous flux at that time to the total luminous flux, and a lamp with a low luminous flux maintenance factor has a short life and is not practical.

  This decrease in the luminous flux maintenance factor is faster in a metal halide lamp that does not enclose mercury than in a metal halide lamp that contains mercury. The former lamp encloses mercury with a low vapor pressure so that the luminous flux rises quickly, while the latter lamp does not encapsulate mercury and thus the luminous flux rises slowly. Therefore, in order to improve the luminous flux rise, the latter lamp needs to be supplied with high power at the time of starting, and the latter lamp has a higher quartz glass tube wall temperature and more easily transmits sodium. Because.

  As described above, the sodium transmission phenomenon has been known as a cause of the decrease in the luminous flux maintenance factor. However, a metal halide lamp that does not enclose mercury has a low luminous flux maintenance factor and has not reached a practical level.

  An object of the present invention is to provide a metal halide lamp that improves the luminous flux maintenance factor while using a discharge medium that essentially does not contain mercury.

In order to achieve the above object, the metal halide lamp of the present invention has a light-transmitting hermetic container having an arc tube portion that forms a discharge space of 0.1 cc or less inside, power is applied to one end, and the other end is A pair of electrodes arranged opposite to each other in the discharge space, and a discharge medium containing a metal halide containing no less than 90 μmol / cc and not more than 150 μmol / cc of sodium halide and a rare gas sealed in the arc tube section And the light emitting tube section is turned on when the tube wall load is 50 (W / cm ² ) or more.

  According to the present invention, a high luminous flux maintenance factor can be maintained even with a discharge medium that essentially does not contain mercury.

(First embodiment)
Embodiments of a metal halide lamp according to the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is an overall view for explaining a first embodiment of a metal halide lamp of the present invention.

  The hermetic container 1 is made of, for example, quartz glass having translucency, and includes a substantially elliptical arc tube portion 11 and sealing portions 121 and 122 provided at both ends in the longitudinal direction thereof. The arc tube portion 11 is formed with a substantially cylindrical discharge space 111 in the longitudinal direction thereof. In this discharge space 111, an electrode 21 made of, for example, tungsten extending from the inside of the sealing portions 121 and 122 is formed. , 22 are arranged so that their tips face each other with a predetermined distance between the electrodes. Although not shown in the figure, power is supplied to these other ends by an external power application means, and arc discharge occurs between the electrodes.

  In addition, the discharge space 111 is filled with metal halides such as sodium iodide, scandium iodide, zinc iodide, and rare gas xenon as a discharge medium. Metal sodium contained in sodium iodide and metal scandium contained in scandium iodide mainly act as luminescent metals, and the metal zinc contained in zinc iodide is mainly a lamp voltage instead of mercury. Acting as a forming medium, xenon acts primarily as a starting gas. In addition, iodine that forms halides is most suitable as a halide because it is less reactive than others.

  Here, mercury is essentially not contained in the discharge space 111. This “essentially” means that it does not contain any mercury or accepts an amount of mercury of less than 2 mg per cc, preferably 1 mg or less. This is because when the voltage of the discharge lamp is increased to a required level by mercury vapor as in the case of a conventional short arc lamp containing mercury, 20-40 mg per 1 cc, and in some cases, 50 mg or more are sealed. This is because the amount of mercury is overwhelmingly small.

  The sealing portions 121 and 122 are plate-like portions formed by being crushed, and metal foils 31 and 32 made of, for example, molybdenum are sealed therein. One end of each of the metal foils 31 and 32 is connected to the sealing portion side of the electrodes 21 and 22 whose tips extend into the discharge space 111 by welding or the like, and the introduction conductors 41 and 42 are welded to the other end. The other end of the introduction conductor 42 extends outside the sealing portion 122 and is connected to one end of the power supply terminal 5 at a substantially right angle. Since the power supply terminal 5 is formed in an L shape, the other end faces in the direction of the introduction conductor 41 and extends substantially parallel to the sealing portions 121 and 122. An insulating tube 6 is attached to a portion of the power supply terminal 5 parallel to these.

  A cylindrical outer tube 7 made of, for example, a material that blocks ultraviolet rays is provided outside the hermetic container 1 including these so as to cover the longitudinal direction thereof. A diameter-reduced portion 71 is formed at both ends of the outer tube 7. The diameter-reduced portion 71 is glass-welded near the end of the sealing portion 122 in the direction of the anti-light emitting tube portion 11. The other diameter-reduced portion that has not been glass-welded near the end of the sealing portion 121 in the direction of the anti-light emitting tube portion 11.

  The outer tube 7 that covers the airtight container 1 is connected to the socket 9 via a metal tool 8 that is formed so as to sandwich the outer peripheral surface thereof. A metal terminal 91 is formed along the outer peripheral surface of the small diameter portion of the socket 9, and the metal terminal 91 is electrically connected to the inside of the power feeding terminal 5 and the socket 9.

FIG. 2 is an enlarged view of the vicinity of the arc tube portion for explaining an example of the specification of the metal halide lamp of FIG. The inner diameter r of the arc tube portion 11 is 2.6 mm, the outer diameter R is 6.0 mm, the maximum length L in the longitudinal direction is 6.5 mm, and the volume of the discharge space 111 formed by these is 0.02 cc, The inter-electrode distance D between the electrodes 21 and 22 arranged opposite to each other on the axis is 4.2 mm. The discharge medium sealed in the arc tube portion 11 contains 0.8 mg of scandium iodide-sodium iodide-zinc iodide as a metal halide, 10 atm of xenon as a rare gas, and does not contain any mercury. This metal halide lamp is lit when the tube wall load indicating the electric power per unit area is 50 W / cm ² or more.

  The reason why the volume of the discharge space 111 is set to 0.1 cc or less is that if the volume is too large, the coldest part temperature in the discharge space 111 is lowered and the light emission efficiency is lowered. Here, the volume of the discharge space 111 is preferably 0.015 cc or more and 0.025 or less. When the volume is within this range, the luminous efficiency is not particularly lowered, and the tube wall temperature of the tubular portion 11 is high. The permeation phenomenon of sodium activated by becoming too much can be suppressed.

The reason why the tube wall load is set to 50 W / cm ² or more is that if the tube wall load is smaller than this value, the initial total luminous flux becomes low, which is not practical. Here, the tube wall load is a rated lamp power per unit inner surface area of the arc tube portion 11.

  FIG. 3 is a graph showing the results of a 1000 hour blinking lighting test in the EU 120 minute mode with the amount of sodium iodide enclosed in the lamp specification of FIG. This test is a life test condition of a metal halide lamp for automobile headlamps established by the Japan Light Bulb Industry Association, and it is said that a lamp that maintains a luminous flux maintenance factor of 80% or more in this test is at a practical level. .

  As can be seen from the figure, the luminous flux maintenance factor is rapidly improved from around 75 μmol / cc to around 90 μmol / cc, and in the middle, the luminous flux maintenance factor exceeds 80% near 85 μmol / cc, and thereafter rises with a gentle gradient to 135 μmol. From around / cc, it is almost saturated. Therefore, it can be said that when the sodium iodide encapsulation amount is less than 90 μmol / cc, the luminous flux maintenance factor rapidly decreases.

  In this test, when the sodium iodide content was 169 μmol / cc or more, a phenomenon of red light emission was observed. This red light emission seems to be related to the amount of sodium enclosed, but this red light emission state is not practical in a metal halide lamp.

  Therefore, the amount of sodium iodide enclosed is preferably 90 μmol / cc or more and 150 μmol / cc or less.

  Here, the amount of sodium iodide encapsulated in the present invention is a suitable range for a metal halide lamp that does not encapsulate mercury that requires high power input at the time of startup in order to improve the rise of the luminous flux. That is, because the quartz glass tube wall temperature and the like are different, it cannot be applied to mercury-containing metal halide lamps having different sodium penetration rates.

  Also, even in lamps with less than 2 mg of mercury per cc, there is no significant difference between the rise of light flux and a metal halide lamp that does not enclose mercury, so that the amount of mercury rises at the same time as when mercury is not encapsulated. It is necessary to input power. Therefore, the range of the amount of sodium iodide sealed according to the present invention is effective in improving the luminous flux maintenance factor even in this case.

  In this embodiment, the amount of sodium iodide enclosed in the arc tube portion 11 of the hermetic container 1 is set to 90 μmol / cc or more and 150 μmol / cc or less, so that in the 1000-hour blinking lighting test in the EU 120-minute mode, Since a high luminous flux maintenance factor of at least% can be maintained, a long-life and practical metal halide lamp can be realized.

  In addition, the range of the amount of encapsulation is not limited to the amount of sodium iodide enclosed, and the same can be said as long as it is a substance that causes sodium permeation, that is, sodium bromide, The effect of the present invention can be obtained even when the total amount of sodium halide enclosed is 90 μmol / cc or more and 150 μmol / cc or less.

The whole figure for demonstrating 1st Embodiment of the metal halide lamp of this invention. FIG. 2 is an enlarged view of the vicinity of an arc tube portion for explaining specifications of the metal halide lamp of FIG. 1. The graph which shows the result of having performed the blinking lighting test in the lamp specification of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Airtight container 11 Arc tube part 111 Discharge space 21, 22 Electrode 31, 32 Metal foil 41, 42 Introducing conductor 5 Feeding terminal 6 Insulating tube 7 Outer tube 8 Metal tool 9 Base

Claims (2)

A translucent airtight container having an arc tube portion that forms a discharge space of 0.1 cc or less inside;
A power is applied to one end, and the other end is a pair of electrodes arranged opposite to each other in the discharge space;
A discharge medium containing a metal halide containing no less than 90 μmol / cc and not more than 150 μmol / cc of sodium halide and a rare gas enclosed in the arc tube portion;
A metal halide lamp characterized by being lit when a tube wall load of the arc tube portion is 50 (W / cm ² ) or more. 2. The metal halide lamp according to claim 1, wherein most of the sodium halide of the discharge medium is made of iodide.

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