JP2000057994A - Double end type low-power metal halide lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lamp for vehicle having excellent light emitting efficiency at a low power by sealing the ScI3-NaI-based metal, and setting the electrode diameter in a specified range in the rated power set in a specified range. SOLUTION: An electrode is structured so that flow-out of the heat from the electrode can be prevented so as to sufficiently raise the temperature of a light emitting tube by setting a diameter Φn of a pair of first electrode and second electrode 20 to be inserted into an arc chamber electrically connected to a molybdenum foil 21 so as to be Φn<=0.25 mm. In the case where the first electrode and the second electrode 20 are respectively formed of an electrode part 22 and an electrode tip part 23, assuming diameter of the electrode part 22 ΦS mm, and diameter of the electrode tip part 23 formed into a spherical shape ΦP mm, and by setting ΦS<=ΦP, since the tip of the electrode is formed into a shape having a cross sectional area to be increased and the heat hardly to flows out, lowering of the light emitting efficiency due to the reduction of the input power can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-ended low-power metal halide lamp for a vehicle, and
Decreasing the luminous efficiency by reducing the input power from 35 W by defining the electrode shape and electrode diameter to keep the temperature inside the arc chamber of the arc tube sufficiently at a rated power of less than 5 watts, especially in the range of 20 to 30 W A double-ended low-power metal halide used for vehicles that maintains the arc tube temperature sufficiently to suppress a reduction in the amount of metal halide evaporation and prevents a reduction in metal spectrum intensity that contributes to light emission. It is about a lamp.

[0002]

2. Description of the Related Art Conventionally, metal halide lamps have been widely used mainly for sports lighting and the like due to their high color rendering properties and high efficiency. In recent years, in response to the demands of the age of energy saving, the efficiency of metal halide lamps has been increased. In particular, recently, development of products with low wattage and compactness has been progressing.

As one example, a 21 W metal halide lamp is used for an endoscope. Since the arc length is 1.2 mm, the efficiency of incidence on the fiber is high. 35W metal halide lamps are beginning to be used in automobile headlights, and are already installed in some models in Europe and Japan. In Europe, the standardization of 35W metal halide lamps for vehicles is progressing, and it is expected that standardization of the standard will be considered in Japan.

The metal enclosed in these low wattage metal halide lamps has a spectral distribution shown in FIG. 4 with the main component ScI ₃ —NaI composition. As described above, a metal halide lamp in which scandium and a halide containing sodium (Sc-Na) as main components are not particularly shown,
It is known that compared to metal halide lamps having a composition of -Tl-In or Dy-Tl- (In), the radiation efficiency in the visible region is higher and higher efficiency can be obtained.

With respect to the composition of ScI _{3 and} NaI, the shape of the arc tube, the encapsulation ratio of the halide and the end structure of the arc tube have been studied, and a 35 W metal halide lamp having an efficiency of 90 lm / W has been developed in recent years.

[0006] These double-ended low-power metal halide lamps are short arc-type metal halide lamps having a relatively short arc length, are close to point light sources, and can provide a large amount of light. In particular, in a 35 W metal halide lamp for a vehicle of this type, since a luminous flux rising is required instantaneously, a rare gas is pressurized and sealed, and an overcurrent flows at the time of starting.

Further, as shown in FIG.
In order to keep the temperature of 1 sufficiently, and to have a temperature enough for the metal halide to evaporate sufficiently, a design for optimizing the heat capacity is designed.

FIG. 5 shows numerical values designed in terms of the shape of the arc tube and the end structure of the arc tube for optimal heat capacity in consideration of their heat insulation effect. The thickness t of the maximum outer diameter portion 62 of the envelope 61 of the arc tube is t> 1.5 mm, and the arc chamber diameter Φa is Φa> 2.6 mm.

In the arc chamber 66 of the arc tube, the distance d between the tip 65 of the electrode forming an arc and the wall 67 of the arc chamber.
Is about d ≧ 1.0.

[0010] The enlarged section _{S g} of silica glass portion of the primary neck 63 and a secondary neck portion 64 of the arc tube shown in Figure 6 (a). FIG. 6B shows an enlarged cross section S of the maximum outer diameter portion 62 of the envelope 61 of the arc tube in FIG. 5 in a plane orthogonal to the longitudinal axis. At this time, the ratio S _g / S =
It is about 0.26.

Let the length of the arc chamber portion of the arc tube be l, take a distance l of the same length from the primary neck portion 63 and the secondary neck portion 64 in the end direction, respectively, and seal the respective sealing portions at that time. Let the volumes of 68 and 69 be V _s1 and V _s2 . When the volume of the bulb 61 of the arc chamber portion and _{V g V} s1 = _V
In _s2 = _73.7mm ³ is a _V g = _95.8mm ^3.

The primary electrode 69 and the secondary electrode 69 have an electrode diameter .PHI. Of 0.25 mm or more, and the electrode shape is cylindrical, and the diameter is substantially the same up to the tip of the electrode. Then, each is electrically connected to the molybdenum foil. Although not specifically shown, the molybd foil has a knife-edge wedge-shaped cross section and a thickness of 2 to avoid airtight sealing and undesirable stress concentration.
The width is set to 1.5 to 2.0 mm, and the length is set to 6 to 8 mm.

As described above, in the conventional 35 W metal halide lamp for a vehicle, only the shape of the arc tube and the end structure of the arc tube are considered, and the shape of the electrodes and the like are as follows.
With only the above-described rules, the temperature of the arc tube was maintained at a temperature at which the metal halide was sufficiently evaporated. However, when designing a metal halide lamp for a vehicle with even lower power, unless the electrode shape and electrode diameter of the electrode structure are newly defined, the luminous efficiency at an input power of less than 35 W is reduced, and the luminescent color is accordingly reduced. Shifts to blue.

This is because, when the input power is further reduced, the amount of evaporation of the metal halide is reduced and the emission intensity of the metal halide is reduced. Normally used S
cI ₃ For -NaI based metal halide lamp, suffer this problem.

[0015]

As described above, in the conventional metal halide lamp for a 35 W vehicle, the temperature was maintained at a level sufficient for the metal halide to evaporate sufficiently. However, it was attempted to design a metal halide lamp with lower power. In this case, if the design parameters of the 35 W metal halide lamp are scaled down as the input power is reduced, the temperature inside the enclosure cannot be maintained satisfactorily, and the evaporation of metal halide decreases, resulting in a decrease in luminous efficiency.
The emission color shifts to blue.

The present invention solves the above-mentioned problems, and realizes a metal halide lamp for a vehicle with lower power and higher luminous efficiency in order to meet the needs of users aiming at energy saving. Further, in a low-power metal halide lamp for a vehicle, an instantaneous luminous flux rising is required.
Must be pressurized and an overcurrent must flow during startup.

The above-mentioned 21 W metal halide lamp does not require an instantaneous rise of a light beam because it is used for an endoscope. In this respect, the design parameters are different from those of the metal halide lamp for vehicles of less than 35 W.

The present invention is a structure of a low power metal halide lamp of less than 35 W capable of instantaneously lighting by pressurizing and sealing Xe and supplying an overcurrent at the time of starting the lamp because an instantaneous luminous flux rising is required. By regulating the electrode diameter and electrode shape with various parameters, it is possible to prevent heat from flowing out from the tip of the electrode, maintain the temperature of the arc tube sufficiently, and prevent a decrease in luminous efficiency due to a decrease in input power. Accordingly, an object of the present invention is to provide a low-power metal halide lamp for a vehicle of less than 35 W, particularly 20 to 30 W.

[0019]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides a double-end type low-power vehicle for a vehicle in which a rare gas (Xe) is pressurized and sealed, an overcurrent is supplied at the time of starting, and an instantaneous luminous flux rise is possible. in a metal halide lamp, when the rated power is less than 35W, it has an encapsulated metal ScI ₃ NaI system, by regulating the electrode diameter and the electrode shape to a new, fully maintaining the temperature of the arc tube, the input power Provided is a double-ended low-power metal halide lamp in which luminous efficiency does not decrease even if it decreases.

The action of sufficiently maintaining the temperature of the envelope of the arc tube of the double-ended low-power metal halide lamp will be described below.
This shows that this is achieved by newly regulating the electrode shape and electrode diameter. When the diameter of the electrode is Φ nmm, Φ n ≦ 0.25 mm for the primary and secondary electrodes of the arc tube. When the electrode is composed of an electrode part and an electrode tip, the electrode part diameter is ΦSmm, and the electrode part tip diameter is ΦPmm.
And ΦS ≦ ΦP.

Further, the shape of the electrode tip may be spherical or
By adopting a columnar shape and increasing the cross-sectional area of the electrode as it approaches the electrode tip, the structure is such that heat does not easily flow out of the electrode tip, preventing heat from flowing out of the electrode, By keeping the temperature of the arc tube sufficiently, it is possible to prevent a decrease in luminous efficiency due to a decrease in input power.

The arc chamber of the envelope of the arc tube has a circular shape, an elliptical shape or a shape close to it, and has a pair of electrodes in which mercury, a rare gas, and at least one kind of metal halide are sealed. ing. A rare gas (Xe) is pressurized and sealed, and an overcurrent is supplied at the time of starting to enable instantaneous rise of a light flux. By doing so, the input power of the double-ended low-power metal halide lamp is reduced to 35
Less than W, even when reduced in particular 20～30W, the temperature of the arc tube can be kept sufficiently, it is possible to prevent a reduction in luminous efficiency due to a decrease in the input power, if the ScI ₃ NaI based metal halide lamp However, we propose a double-ended low-power metal halide lamp for vehicles that does not shift the emission color.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The electrode structure of the present invention for sufficiently maintaining the temperature of the envelope of the arc tube will be described with reference to examples. Electrode uses a tungsten (W-1.7% Th0 ₂ containing). The shape of the arc tube and the end structure of the arc tube of the metal halide lamp for vehicles (hereinafter referred to as a double-ended low-power metal halide lamp) of less than 35 W shown in FIG. 1 are as described by the present inventors in Japanese Patent Application No. 10-195647. , It is regulated. Details will be described later.

FIGS. 2A to 2D show the electrode structure of a double-ended low-power metal halide lamp of less than 35 W according to the present invention. The electrode structure shown in FIG.
When the diameter of a pair of the first electrode and the second electrode 20 inserted into the arc chamber 6 having an electrical connection with 1 is Φn, by setting Φn ≦ 0.25 mm, the flow of heat from the electrodes can be reduced. Prevent,
The temperature of the arc tube can be sufficiently maintained.

The electrode structure shown in FIG.
When a pair of the first electrode and the second electrode 20 inserted into the arc chamber 6 having an electrical connection with 1 are formed from the electrode portion 22 and the electrode tip portion 23, respectively, the diameter of the electrode portion 22 is ΦSmm. When the diameter of the electrode tip portion 23 is spherical when ΦPmm, by setting ΦS ≦ ΦP, the electrode has a shape in which the cross-sectional area of the tip is large and has a structure in which heat hardly flows out. A decrease in luminous efficiency due to a decrease in power can be prevented.
The diameter of the electrode tip 23 is ΦP ≦ 0.25 m
m.

The electrode structure shown in FIG.
A pair of first electrode and second electrode 20 inserted into the arc chamber 6 having an electrical connection with the
3, the diameter of the electrode portion 22 is ΦYmm, and the diameter of the electrode tip portion 23 when it is cylindrical is ΦXmm.
By setting ΦY ≦ ΦX, the first electrode and the second electrode 20 have a shape in which the cross-sectional area of the tip is large and have a structure in which heat hardly flows out. Drop can be prevented. When the diameter of the electrode tip 23 is ΦX, ΦX ≦ 0.25 mm.

The electrode structure shown in FIG.
The cross-sectional area of the pair of first and second electrodes 20 inserted into the arc chamber 6 having an electrical connection with
, The electrode has a shape in which the cross-sectional area of the tip increases, and has a structure in which heat hardly flows out. If the diameter of the electrode tip 23 at this time is ΦK, then ΦK ≦ 0.25 mm.

As described above, by restricting the structure of the electrode as shown in FIGS. 2A to 2D, heat is prevented from flowing out from the electrode tip portion and the entire electrode, and the envelope 1 of the arc tube is formed. The temperature can be maintained at a temperature at which the metal halide is sufficiently evaporated. The shape of the envelope and the structure of the edge of the envelope at that time are as regulated by the present inventor in Japanese Patent Application No. 10-195647. Hereinafter, the regulated values will be briefly described with reference to FIG.

First, the maximum outer diameter portion 2 of the envelope 1 of the arc tube
Is defined as t mm and the maximum inner diameter of the arc chamber 6 of the envelope 1 is defined as Φamm, t ≦ 1.5 and Φa ≦ 2.6 are regulated. As a result, the temperature of the arc tube can be sufficiently maintained, and a decrease in luminous efficiency due to a decrease in input power can be prevented.

Second, an arc-forming electrode tip 5 and an arc chamber wall 7 in an arc chamber 6 of the envelope 1 in the arc tube.
Is defined as 0.6 mm ≤ d ≤ 1.3 mm, where d is the distance.

The reason for setting the distance d between the electrode tip 5 and the arc chamber wall 7 to 1.3 mm or less is that heat is prevented from flowing out of the sealing body 1 and the temperature of the arc tube is sufficiently maintained to reduce the input power. This is because it is possible to prevent a decrease in luminous efficiency due to light emission. Further, the reason why the thickness is 0.6 mm or more is that it is possible to prevent arc instability and to prevent extinguishing.

[0032] Thirdly, perpendicular to the cross-sectional area S _g of the primary neck 3 and the quartz glass of the secondary neck portion 4 of the arc tube, the longitudinal axis of the maximum outer diameter 2 of the bulb 1 of the arc tube The ratio S _g /S≦0.85 of the cross-sectional area S on the surface to be formed is regulated. Preferably, 0.15 ≦ S _g /S≦0.25 and the vest ratio is around 0.2. By maintaining this ratio, it is possible to prevent heat from flowing out of the sealing body 1 and to maintain the temperature of the arc tube sufficiently, thereby preventing a decrease in luminous efficiency due to a decrease in input power.

Fourth, a distance 1 equal to the length 1 from the primary neck portion 3 to the secondary neck portion 4 is taken from the primary neck portion 3 and the secondary neck portion 4 to the end portions of the arc tube, respectively. the volume of sealing part 8 at that time _{(V s1} and _{V s2),} respectively the envelope 1 by volume with the distance from the primary neck 3 to the secondary neck portion 4 a _{(V g),} 0.4V _g By setting <V _s1 , V _s2 <0.9 V _g , it is possible to prevent heat from flowing out of the sealing body 1 and prevent a decrease in luminous efficiency due to a decrease in input power by sufficiently maintaining the temperature of the arc tube. And 0.4V
preventing excessive temperature rise of the sealing portion 8 by a _g, the sealing portion 8
Leakage of the sealed gas or the like can be prevented.

In the above-described double-ended low-power metal halide lamp, the arc chamber 6 has a circular or elliptical shape or a shape similar thereto, and a pair of electrodes 9 are provided in the arc chamber 6.
And has enclosed therein mercury, a rare gas, and at least one or more metal halides.

The metal halide to be sealed is ScI
₃ and NaI, and the encapsulation ratio is ScI ₃ : NaI = 3: 1 to 1: 8 in terms of weight ratio. Then, in order to use as a lamp for a vehicle requiring an instantaneous luminous flux rising, a rare gas (Xe) is pressurized and sealed, and an overcurrent flows at the time of starting.

Although the arc tube shape and the end structure of the arc tube alone can sufficiently exert their effects, it is disclosed in Japanese Patent Application No. 10-195647 that various effects can be further exerted by combining them. As mentioned.

In the 35 W metal halide lamp, the temperature of the arc tube was maintained at a temperature at which the metal halide was sufficiently evaporated. However, when designing a metal halide lamp for a vehicle with even lower power, if the electrode shape and the electrode diameter such as the electrode structure are not newly defined, 35 W
The luminous efficiency at an input power of less than is reduced, and the luminescent color shifts to blue accordingly.

As described above, not only the shape of the arc tube and the end structure of the arc tube but also the shape of the electrode are regulated, so that heat can be prevented from flowing out from the tip of the electrode, and the temperature of the arc tube can be reduced. Can be sufficiently maintained, and a decrease in luminous efficiency due to a decrease in input power can be prevented. This is less than 35W, especially 2
It is effective for a low power metal halide lamp for vehicles of 0 to 30W. In FIG. 3, the sectional area of the electrode tip is 0.2
5 mm or less, the diameter of the electrode portion is smaller than the tip of the electrode, and the power of the double-ended low-power metal halide lamp when the envelope and the end structure of the envelope are regulated as disclosed in Japanese Patent Application No. 10-195647. Luminous efficiency characteristics are shown by solid lines.
The broken line shows the power-luminous efficiency characteristics of the conventional 35 W metal halide lamp. It shows a luminous efficiency of 60 to 90 lm / W despite the decrease in power.

[0039]

The metal halide lamp for a conventional 35 W vehicle has a temperature sufficient for the metal halide to sufficiently evaporate. However, if the temperature is less than 35 W, the temperature of the sealing body is reduced, and the evaporation of the metal halide is reduced. As a result, the luminous efficiency decreases.

According to the present invention, in the case of a double-ended low-power metal halide lamp, especially when the power is set to less than 35 W for a vehicle, the design parameters of the metal halide lamp for a 35 W vehicle are scaled down according to the input power.
When the encapsulated metal halide is ScI ₃ and NaI, the luminous efficiency decreases and the luminous color shifts to blue. Therefore, by newly regulating the shape and structure of the electrode, the luminous tube temperature is sufficiently maintained to prevent the luminous efficiency from lowering. can do.

Further, the shape and structure of the electrode are newly regulated,
A rare gas is charged under pressure, the charged metal halides are made of ScI ₃ and NaI, and an overcurrent is applied at the time of starting, whereby 35
Even with an input power of less than W (in particular, 20 to 30 W), instantaneous luminous flux rising is enabled. Further, these effects are further improved by a combination of the setting parameters.

[Brief description of the drawings]

FIG. 1 is a front view and a sectional view showing an embodiment of a double-ended low-power metal halide lamp according to the present invention.

FIG. 2 (a) is a view showing an electrode shape of a first embodiment of the double-ended low-power metal halide lamp of FIG. 1;

FIG. 2 (b) is a view showing an electrode shape of a second embodiment of the double-ended low-power metal halide lamp of FIG. 1;

FIG. 2C is a view showing an electrode shape of a third embodiment of the double-ended low-power metal halide lamp of FIG. 1;

FIG. 2D is a view showing an electrode shape of a fourth embodiment of the double-ended low-power metal halide lamp of FIG. 1;

FIG. 3 is a graph showing power-luminous efficiency characteristics of a double-ended low-power metal halide lamp according to the present invention and a conventional 35W type.

FIG. 4 shows the spectral distribution of a metal halide lamp having a composition of ScI ₃ —NaI.

FIG. 5 shows a front view and a cross-sectional view of a conventional double-ended low-power metal halide lamp.

6 (a) is an enlarged sectional view of a quartz glass portion of a primary neck portion and a secondary neck portion of the arc tube in FIG.

6 (b) is a view showing an enlarged cross section S in a plane orthogonal to the longitudinal axis at the maximum outer diameter portion of the envelope of the arc tube in FIG.

[Explanation of symbols]

Primary electrode, secondary electrode: 9, 20, 69 Electrode diameter: Φn Electrode part: 22 Electrode part diameter: ΦX, ΦS, electrode tip part: 23 Electrode tip part diameter: ΦY, ΦP, ΦK Molyb foil: 21, sealing Body: 1,61 Enclosure maximum outer diameter: 2,62 Primary neck: 3,63 Secondary neck: 4, 64 Electrode tip: 5, 65 Arc chamber: 6, 66 Arc chamber wall: 7, 67 sealing portion ... 8,68 t ... envelope maximum outer maximum inner diameter d ... electrode tip of the thick .PHI.a ... arc chamber diameter and the distance S g _... 1 primary neck of the arc chamber inner wall and the secondary neck portion S: cross-sectional area in the plane perpendicular to the longitudinal axis at the maximum outer diameter of the sealing body l: length from primary neck, secondary neck to end and length of primary neck length _{V s1,} V s2 ... ₁ primary neck up secondary neck portion from parts, respectively from the secondary neck portion end The volume of the bulb from the volume V g _... each primary neck portion of the sealing portion to the second neck portion when taking an equal distance l to the direction

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[Procedure amendment]

[Submission date] September 20, 1999 (1999.9.2)
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[Procedure amendment 1]

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[0019]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides a double-end type low-power vehicle for a vehicle, in which a rare gas (Xe) is pressurized and sealed, an overcurrent flows at start-up, and an instantaneous light speed rise is possible. A metal halide lamp with a rated power of 35W
When less than, have a sealed metal ScI ₃ NaI system, by regulating the electrode diameter and the electrode shape to a new, fully maintaining the temperature of the arc tube, decrease luminous efficiency input power is also decreased Not provide double-ended low power metal halide lamps.

[Procedure amendment 10]

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[0019]

SUMMARY OF THE INVENTION In view of the above problems, the present invention is directed to a double-ended low-power metal halide lamp in which a rare gas (Xe) is pressurized and sealed, an overcurrent flows at start-up, and an instantaneous light speed rise is possible. There, when the rated power is less than 35W, has an encapsulated metal ScI ₃ NaI system, by regulating the electrode diameter and the electrode shape to a new, fully maintaining the temperature of the arc tube, the input power decreases This makes it possible to use a double-ended low-power metal halide lamp that does not lower the luminous efficiency for vehicles.

[Procedure amendment 11]

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The following shows that the action of sufficiently maintaining the temperature of the arc tube of the double-ended low-power metal halide lamp can be achieved by newly regulating the electrode shape and electrode diameter. In a double-ended low-power metal halide lamp, for a vehicle and rated power is less than 35W,
One end of the arc tube sealed at both ends is a primary neck portion and the other is a secondary neck portion, and the shape inside the arc tube has a circular shape, an elliptical shape or a shape close thereto, and opposes to project into the arc tube. When one of the pair of electrodes is a primary electrode and the other is a secondary electrode, the diameters of the primary electrode and the secondary electrode protruding into the arc tube are Φn, and Φn ≦ 0.25 mm. The primary electrode and the secondary electrode each comprise a portion having a predetermined length protruding from the arc tube and an electrode tip for arc discharge, and the portion having the predetermined length maintains a constant diameter. It is a cylindrical electrode. The electrode diameter is ΦS, the electrode diameter at the tip of the electrode is ΦP, and ΦS ≦ ΦP.

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Further, the electrode tip may be spherical or cylindrical, or the primary electrode and the secondary electrode may each have a predetermined length protruding from the arc tube and an electrode tip for arc discharge. The part having the predetermined length has a structure in which the electrode cross-sectional area increases toward the electrode tip, so that heat is more difficult to flow out of the electrode tip, and the electrode By preventing the outflow of heat and maintaining the temperature of the arc tube sufficiently, it is possible to prevent a decrease in luminous efficiency due to a decrease in input power.

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The inside of the arc tube has a circular shape, an elliptical shape or a shape close to it, and mercury, a rare gas, and at least one or more metal halides are sealed in the arc tube. A rare gas (Xe) is pressurized and sealed, and an overcurrent is supplied at the time of starting to enable instantaneous rise of a light flux. By doing so, even when the input power of the double-ended low-power metal halide lamp is reduced to less than 35 W, particularly 20 to 30 W, the temperature of the arc tube can be sufficiently maintained, and the luminous efficiency due to the reduction of the input power can be maintained. Can be prevented from decreasing, and Sc
Even in the case of I ₃ NaI based metal halide lamp is a double-ended low-power metal halide lamp without emission color shifts can be used for vehicles.

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[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An electrode structure for sufficiently maintaining the temperature of the arc tube according to the present invention will be described below with reference to embodiments. The electrodes are
Tungsten (W-1.7% containing ThO ₂ ) is used. Fig. 2 shows a double-end type low-power metal halide lamp which is less than 35W and which can be used instantaneously for a vehicle and which is shown in Fig. 1. It is assumed that the shape of the arc tube and the end structure of the arc tube are regulated as shown in Japanese Patent Application No. 10-195647 by the present inventor. Details will be described later.

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FIGS. 2A to 2D show the electrode structure of a double-ended low-power metal halide lamp of less than 35 W according to the present invention. The electrode structure shown in FIG.
1 has a pair of opposing electrodes inserted into an arc tube (hereinafter referred to as arc chamber 6) having an electrical connection with the first and second electrodes, one being a primary electrode and the other being a secondary electrode. When φn ≦ 0.25 mm, it is possible to further prevent the outflow of heat from the electrode and sufficiently maintain the temperature of the arc tube.

[Procedure amendment 16]

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The electrode structure shown in FIG.
1 has a pair of opposing electrodes inserted into an arc chamber 6 having an electrical connection with one, one of which is a primary electrode and the other is a secondary electrode, and each of the primary and secondary electrodes 20 has a predetermined length. It has a portion (hereinafter referred to as an electrode portion 22) and an electrode tip portion 23 for arc discharge. At this time, if the diameter of the electrode portion 22 is ΦSmm and the diameter (diameter) when the electrode tip portion 23 is spherical is ΦPmm, then the electrode has a shape in which the cross-sectional area of the tip is increased by ΦS ≦ ΦP. In addition, since it has a structure in which heat hardly flows out, a decrease in luminous efficiency due to a decrease in input power can be prevented. The diameter of the electrode tip 23 is ΦP ≦ 0.25 mm.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kimihiro Itono 1-3-1 Edanishi, Aoba-ku, Yokohama-shi, Kanagawa F-term in Stanley Electric Co., Ltd. Technical Research Institute 5C015 JJ04 QQ03 QQ14

Claims (8)

[Claims] In a double-ended low-power metal halide lamp, when a rated power is less than 35 watts, and when an electrode structure has an electrode diameter of Φn, a primary electrode of an arc tube,
A double-ended low-power metal halide lamp, wherein Φn ≦ 0.25 mm in the secondary electrode. 2. The method according to claim 1, wherein when the electrode structure comprises an electrode portion and an electrode tip portion, the electrode portion diameter is ΦS, the electrode portion tip diameter is ΦP, and ΦS ≦ ΦP. Double-ended low-power metal halide lamp. 3. The double-ended low-power metal halide lamp according to claim 1, wherein the shape of the electrode tip is spherical or cylindrical. 4. The double-ended low-power metal halide lamp according to claim 1, wherein the electrode structure has an electrode cross-sectional area that increases toward the electrode tip. 5. The arc chamber of the envelope of the arc tube has a circular shape, an elliptical shape or a shape similar thereto, and has a pair of electrodes in which mercury, a rare gas, and at least one metal halide are contained. 5. An enclosed structure.
The described double-ended low-power metal halide lamp. 6. The method according to claim 1, wherein the metal halide is ScI ₃ and NaI.
The double-ended low-power metal halide lamp according to claim 5, comprising: 7. The low power metal halide lamp according to claim 5, wherein said rated power is 20 to 30 watts. 8. The double-ended low-power metal halide lamp according to claim 6, wherein the rare gas is pressurized and sealed, and an instantaneous luminous flux rise is made possible by flowing an overcurrent at the time of starting.