JP2006344579A - Double tube type metal halide lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress cracking of a sealing part in a dual tubular type metal-halide lamp. <P>SOLUTION: In the dual tubular type metal-halide lamp, at least a translucent outer tube is arranged so as to surround at least a light-emitting tubular part 11 at the outside of a translucent air-tight container 1 having the light-emitting tubular part 11 that has an electric discharge medium sealed inside, and the air-tight container 1 and the outer tube 7 are mutually joined by dissolving each other's one part, while a relationship between a thermal expansion coefficient a1 of the air-tight container 1 and a thermal expansion coefficient a2 of the outer tube 7 is 1.25≤a2/a1≤1.55. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a double-pipe metal halide lamp used for automobile headlamps and the like.

An arc tube having a pair of electrodes is provided coaxially on the glass tube inside the cylindrical glass tube, and ring-shaped support members are provided on both sides of the arc tube, and the glass tube and the support member are welded together. Thus, the arc tube and the glass tube are integrated, and the difference between the thermal expansion coefficient between the arc tube and the support member and the thermal expansion coefficient between the glass tube and the support member is 10 × 10 ⁻⁷ / ° C. or less. There is a lamp invention. That is, conventionally, other members are used to connect the internal arc tube and the external glass tube. (For example, Patent Document 1)
In contrast, at the present time, when connecting the inner arc tube and the outer glass tube, other end portions of the outer glass tube are sealed to the inner hermetic container, for example, by shrink sealing. In general, a method of performing a strong integral connection without interposing members is used.

Japanese Patent Laid-Open No. 7-78596

  In a double-pipe metal halide lamp in which the inner and outer glass tubes are integrally connected without interposing other members, there is a problem of cracks entering a sealing portion where electrodes and the like are sealed. Therefore, as a result of various verifications by the present inventors on this crack, the inventors have found out that the occurrence of cracks is related to the thermal expansion coefficient of the sealing portion and the outer tube, and have proposed.

  In addition, in the discharge lamp of the said patent document 1, although there is description of the crack by the thermal strain between a glass tube and a supporting member, the crack of this invention is so strong that an inner and outer glass tube is melted. Since this is a problem that occurs for the first time in a lamp having a connected structure, it is an invention that differs from Patent Document 1.

  An object of this invention is to provide the double tube | pipe type metal halide lamp which a crack does not produce easily in a sealing part.

  In order to achieve the above object, the double tube type metal halide lamp of the present invention surrounds at least the arc tube portion outside the translucent airtight container having the arc tube portion in which the discharge medium is sealed. In the double-tube type metal halide lamp in which a translucent outer tube is disposed, the hermetic container and the outer tube are joined by melting a part of each other, and the thermal expansion coefficient a1 of the hermetic container. And the thermal expansion coefficient a2 of the outer tube is 1.25 ≦ a2 / a1 ≦ 1.55.

  ADVANTAGE OF THE INVENTION According to this invention, the crack of a sealing part can be suppressed in a double tube | pipe type metal halide lamp.

(First embodiment)
Hereinafter, a double-pipe 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 double tube type metal halide lamp according to the present invention, and FIG. 2 is a view for explaining a joining relationship between an airtight container and an outer tube according to the present invention. is there.

  The hermetic container 1 is made of, for example, a fire-resistant and light-transmitting quartz glass tube, and is positioned at a substantially central portion of the tube axis, and has a light-emitting tube portion 11 having an approximately elliptical shape in the axial direction and positions at both ends thereof. And plate-shaped sealing portions 121 and 122. A discharge space 13 having a substantially cylindrical shape in the axial direction is formed inside the arc tube 11, and the discharge space 13 is mainly composed of metal halides such as sodium iodide, scandium iodide, zinc iodide, In addition, a rare gas xenon is enclosed as a discharge medium. In addition, although the internal volume of the discharge space 13 shall be 0.1 cc or less, when comprising for motor vehicles, it is desirable that it is 0.01 cc-0.03 cc.

  The encapsulated discharge medium will be described. Metallic sodium contained in sodium iodide and metallic scandium contained in scandium iodide mainly act as a luminescent metal, and metallic zinc contained in zinc iodide. Mainly acts as a lamp voltage forming medium instead of mercury. In addition to these metal halides, cesium metal halides, indium metal halides, tin halides, and the like may be added. These metals are preferably combined with iodine, which is less reactive among halides, but other halides such as bromine and chlorine may be used, or multiple halides may be used in combination. You may do it. Also, the rare gas xenon mainly acts as a starting gas because of its high luminous efficiency immediately after starting.

  Note that mercury is essentially not contained in the discharge space 13. This “essentially free of mercury” 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 amount is compared with the amount of mercury of 20 to 40 mg per 1 cc (which may be enclosed in 50 mg or more in some cases) that was enclosed in the conventional short arc type mercury-containing metal halide lamp. This is because the amount of mercury less than 2 mg allowed in a metal halide lamp is overwhelmingly small, and it can be said that essentially no mercury is contained.

  Metal foils 21 and 22 made of, for example, molybdenum are sealed inside the sealing portions 121 and 122 so that the flat surfaces thereof are parallel to the flat surfaces of the sealing portions 121 and 122. For example, electrodes 31 and 32 made of tungsten metal mixed with thorium oxide are connected to one end of the metal foils 21 and 22 by welding. The electrodes 31 and 32 have a stepped shape in which the distal end side has a larger diameter than the proximal end side, and the distal end side having the larger diameter maintains a predetermined distance between the electrodes in the discharge space 13. And are arranged so that the tips of each other face each other. 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.

  For example, one end of external lead wires 41 and 42 made of molybdenum is connected to the other end of the metal foils 21 and 22 by welding or the like. The other end side of the external lead wires 41, 42 extends to the outside of the sealing portions 121, 122, and the external lead wire 42 that extends in the outward direction of the sealing portion 122 is formed in an L shape. One end of the power supply terminal 5 is connected. A part of the power supply terminal 5 is covered with an insulating tube 6 made of ceramic or the like so that the potential of the external lead wire 42 is not affected.

  A cylindrical outer tube 7 is provided on the outer side of the hermetic container 1 having these components so as to cover at least the arc tube part 11, preferably the most part of the hermetic container 1 along the longitudinal direction thereof. The outer tube 7 and the airtight container 1 are joined portions formed at both end portions of the outer tube 7 by melting and joining a part of each other in the glass tube portion outside the tube axis direction of the sealing portions 121 and 122. 71 and 72 are connected. In addition, the joining state of these joining parts 71 and 72 is a state in which the glass of the airtight container 1 and the glass of the outer tube 7 are almost completely mixed so that the boundary between each other cannot be confirmed as shown in the drawing. In order to form such a joined state, the airtight container 1 and the outer tube 7 are brought into contact with each other and then heated to fuse each other.

The outer tube 7 is made of quartz glass with at least one of TiO ₂ (titanium oxide), CeO ₂ (cerium oxide), Al ₂ O ₃ (aluminum oxide), K ₂ O (potassium oxide), BaO (barium oxide), Alternatively, a plurality of metal oxides are added to form a light transmitting and ultraviolet blocking property. That is, the hermetic container 1 and the outer tube 7 are made of materials having different thermal expansion coefficients. In the present invention, if the thermal expansion coefficient a1 of the hermetic container 1 and the thermal expansion coefficient a2 of the outer pipe 7 are given, a2 / The relationship of a1 is configured to satisfy 1.25 ≦ a2 / a1 ≦ 1.55. The value of a2 / a1, which is the ratio of each thermal expansion coefficient, changes the addition amount, addition balance, etc. of TiO ₂ , CeO ₂ , Al ₂ O ₃ , K ₂ O, BaO to be added to the outer tube 7, and the thermal expansion It can be increased or decreased by changing the coefficient a2.

  The space 73 sealed by the outer tube 7 and the airtight container 1 can be filled with an inert gas such as nitrogen or argon, or can be in a vacuum atmosphere. By adopting these configurations, it is possible to make it difficult to contain moisture, which is considered to affect the life characteristics. In addition, when the space 73 is an atmosphere having a low thermal conductivity such as an argon atmosphere or a vacuum, the temperature of the arc tube portion 11 is kept high, so that the luminous efficiency can be improved.

  A socket 8 is connected to the sealing portion 121 side of the outer tube 7 in a state where the hermetic container 1 is covered by a fixed metal tool 9 attached to the outer peripheral surface of the outer tube 7. A metal terminal 81 for supplying power from the lighting circuit is formed along the outer peripheral surface of the end portion of the socket 8, and the metal terminal 81 is electrically connected to the external lead wire 42 via the power supply terminal 5. Connected. Although not shown, the other terminal electrically connected to the external lead wire 41 side is formed at the bottom portion of the socket 8.

  The double tube type metal halide lamp constituted by these is lit at about 35 W at the time of stability, and at about 75 W of about twice the power at the time of stabilization in order to accelerate the rise of the luminous flux at the time of starting.

  FIG. 3 is an enlarged view for explaining the specifications and the like of the double tube type metal halide lamp of FIG. The volume of the discharge space 13 is 0.03 cc, the inner diameter A of the arc tube portion 11 is 2.6 mm, the outer diameter B is 6.2 mm, the maximum length C in the longitudinal direction is 7.8 mm, and the distance D between the electrodes is 4.2 mm. is there. The diameters of the large diameter portions of the electrodes 31 and 32 are 0.38 mm, the diameter of the small diameter portion is 0.30 mm, and the diameters of the external lead wires 41 and 42 are 0.40 mm. The arc tube portion 11 has 0.23 mg of scandium iodide, which is a metal halide as a discharge medium, 0.37 mg of sodium iodide, 0.09 mg of zinc iodide, 0.001 mg of indium bromide, cesium iodide. 0.008 mg, 10 atm of xenon, which is a rare gas, is enclosed, and mercury is not contained at all. The space 73 is filled with 0.7 atm of inert gas argon.

  FIG. 4 is a diagram for explaining a difference in the amount of elongation at the time of lighting when the ratio a2 / a1 of the thermal expansion coefficient between the sealing portion and the outer tube is changed in the lamp specification of FIG. Here, the + direction on the vertical axis in the figure indicates a state in which the airtight container extends more than the outer tube, and the − direction indicates the opposite state. The thermal expansion coefficient ratio a2 / a1 is calculated by the thermal expansion coefficient when the temperature of each glass is 500 ° C.

  From FIG. 4, the difference in elongation is 0 when a2 / a1 is about 1.41, and before or after that, either the sealing part or the outer tube may be in an extended state. Recognize. In addition, when the material of a sealing part and an outer tube is the same, ie, a2 / a1 = 1, it turns out that the airtight container 1 is expanded largely with respect to the outer tube 7, and it is not a suitable condition.

  As described above, a2 / a1 = 1 is not the best condition, and the reason why the difference in the thermal expansion coefficient between the sealing portions 121 and 122 and the outer tube 7 is better is the reason for both during lighting. It is in the temperature difference. When the temperature of the outer tube 7 portion and the temperature of the upper portion of the arc tube portion 11 at the point Z in FIG. 3 are measured at the time of lighting, the outer tube 7 is 550 to 650 ° C., and the upper portion of the arc tube portion 11 is 900 to 1000 ° C. It was confirmed that the difference in temperature was 250 ° C to 450 ° C. In other words, in a lamp that does not enclose mercury that is lit at a high load in order to improve luminous flux rise and luminous efficiency, and in a lamp that has a space 73 in an argon atmosphere to increase thermal efficiency, a large temperature difference occurs between the inside and outside glass during lighting. It is easy to assume that a difference occurs due to the temperature difference during lighting.

  FIG. 5 is a graph for explaining the strain state and the crack occurrence rate when the flash test in the EU 120 minute mode, which is the life test condition of a metal halide lamp for automobile headlamps, established by the Japan Light Bulb Industry Association is performed for 1500 hours. FIG. Here, “strain” is generated in the vicinity of the sealing portions 121 and 122 where the metal foils 21 and 22 are sealed, and × (bad) based on the observation result using a strain inspector. ) To ◎ (good). Here, the distortion tester is a device that discriminates distortion by detecting the optical path difference generated by the strain distribution of the glass part to be observed, and changes the color tone of the sensitive color field by using sensitive color removal. From the above, it is possible to observe stresses such as the compression direction and the tensile direction and their strengths. In addition, the number of lamp tests in FIG.

  From the results, when a2 / a1 ≦ 1.2 and a2 / a1 ≧ 1.6, the sealing portions 121 and 122 are strongly distorted and the crack generation rate is high, but the other a2 / It can be seen that at a1, the strain is relaxed and the crack generation rate is lowered accordingly. Therefore, if 1.25 ≦ a2 / a1 ≦ 1.55, the rate of occurrence of strain and cracks can be effectively suppressed. Further preferably, 1.3 ≦ a2 / a1 ≦ 1.5.

  Here, the generation mechanism of a crack is estimated as follows.

  As an extreme example, let us consider a case where the hermetic container 1 does not thermally expand and only the outer tube 7 expands greatly. In this case, when the outer tube 7 is thermally expanded, the outer tube 7 forcibly pulls the hermetic container 1 outward through the joints 71 and 72 so that the outer tube 7 expands. Therefore, a tensile stress is applied to the hermetic container 1 and distortion occurs. And when this distortion is strong, it is thought that the sealing parts 121 and 122 with comparatively weak intensity | strength in the airtight container 1 cannot endure stress, and the crack generate | occur | produced. On the contrary, the outer tube 7 does not thermally expand at all, and even when only the hermetic container 1 is thermally expanded, when the heat expands, the sealing portions 121 and 122 try to expand the outer tube 7 by the joint portions 71 and 72. Therefore, the airtight container 1 is distorted, and cracks are generated in the sealing portions 121 and 122 according to the strength. Needless to say, when the hermetic container 1 and the outer tube 7 are evenly extended by heat, distortion does not occur, and no cracks are generated.

  Therefore, in the present embodiment, in the double tube type metal halide lamp, the relationship between the thermal expansion coefficient a1 of the sealing portions 121 and 122 and the thermal expansion coefficient a2 of the outer tube 7 is 1.25 ≦ a2 / a1 ≦ 1. .55 can alleviate the distortion of the hermetic container 1 and suppress the occurrence of cracks in the sealing portions 121 and 122.

Further, the outer tube 7 is configured such that at least one or more metal oxides of TiO ₂ , CeO ₂ , Al ₂ O ₃ , K ₂ O, and BaO are added, so that the transmittance is not lowered. It is possible to provide a double tube type metal halide lamp that blocks ultraviolet rays harmful to the human body.

  Furthermore, the space 73 formed between the hermetic container 1 and the outer tube 7 can be configured so as not to contain moisture in the space 73 by being in a vacuum state or a state in which gas is sealed. In such a case, improvement in luminous efficiency can be expected.

BRIEF DESCRIPTION OF THE DRAWINGS The whole figure for demonstrating 1st Embodiment of the double tube | pipe type metal halide lamp of this invention. The figure for demonstrating the joining relationship of the airtight container of this invention, and an outer tube | pipe. The enlarged view for demonstrating the example of the specification of the double tube | pipe type metal halide lamp of FIG. The figure for demonstrating the difference of elongation amount when changing ratio a2 / a1 of the thermal expansion coefficient of a sealing part and an outer tube | pipe in the lamp specification of FIG. The figure for demonstrating the state of a distortion when the blink test of EU120 minute mode is done for 1500 hours, and a crack generation rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Airtight container 11 Arc tube part 121,122 Sealing part 13 Discharge space 21,22 Metal foil 31,32 Electrode 41,42 External lead wire 5 Feed terminal 6 Insulation tube 7 Outer tube 71,72 Joint part 73 Space 8 Socket 9 Fixed metal fixture

Claims (5)

In a double-tube type metal halide lamp in which a light-transmitting outer tube is disposed outside a light-transmitting hermetic container having a light-emitting tube portion in which a discharge medium is enclosed, so as to surround at least the light-emitting tube portion. ,
The hermetic container and the outer tube are joined by dissolving a part of each other, and the relationship between the thermal expansion coefficient a1 of the hermetic container and the thermal expansion coefficient a2 of the outer tube is 1.25 ≦ a2. /A1≦1.55, A double tube type metal halide lamp.   2. The double-tube metal halide lamp according to claim 1, wherein a temperature difference between the arc tube portion during lighting and the outer tube is 250 ° C. or more and 450 ° C. or less.   3. The double tube metal halide lamp according to claim 1, wherein mercury is essentially not contained in the discharge medium. The at least one metal oxide of TiO ₂ , CeO ₂ , Al ₂ O ₃ , K ₂ O, and BaO is added to the outer tube. The double tube type metal halide lamp according to any one of the above. The double pipe according to any one of claims 1 to 4, wherein a space formed between the hermetic container and the outer pipe is in a state in which gas is sealed or in a vacuum state. Type metal halide lamp.

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