JP4719105B2 - Metal halide lamp - Google Patents

Description

  The present invention relates to a metal halide lamp which is essentially free of mercury and is used for automobile headlamps and the like.

  A metal halide lamp not containing mercury (hereinafter referred to as mercury-free lamp) is known, for example, from JP-A-2005-339999 (hereinafter referred to as Patent Document 1). In this mercury-free lamp, by combining a metal halide and a rare gas, characteristics equal to or higher than those of a metal halide lamp containing mercury (hereinafter referred to as a mercury-containing lamp) can be obtained without using mercury. It has become.

  As described in Patent Document 1, in a mercury-free lamp, a leak (hereinafter referred to as a crack leak) due to generation of a crack in a sealed electrode portion and a change in chromaticity due to penetration of a discharge medium may easily occur. Are known. In response to this problem, in the present invention, a coil is wound around a predetermined electrode axis region at a coil pitch of 100%. In addition, the crack leak described in patent document 1 means the axial leak generate | occur | produced in the sealing glass part which contacts the electrode shaft in which the coil is not wound.

JP 2005-339999 A JP-A-10-223175 JP 2001-6617 A

  However, when the coil pitch is close to 100% as in Patent Document 1, the discharge medium actually enters the sealing portion along the electrode axis regardless of the length of the electrode shaft in contact with the sealing portion. It was found that leaks (hereinafter referred to as foil leaks) and chromaticity changes due to cracks caused by peeling of the metal foil from the sealing glass are likely to occur.

  Therefore, the present inventor conducted verification by paying attention to the coil pitch and the like. As a result, it was found that the invasion of the discharge medium can be suppressed by winding the coil so that the sealing portion and the electrode shaft are in contact with each other between adjacent coils. However, it has been found that crack specifications (hereinafter referred to as inter-coil leakage) tend to occur in the electrodes between the sealed coils in such a coil specification. Therefore, as a result of further verification, it has been found that if the arithmetic average roughness Ra of the electrodes in contact with the sealing portion between the coils is set to a suitable value, leakage between the coils can be suppressed at the same time, and the present invention has been proposed.

  In addition, in JP-A-10-223175 (hereinafter referred to as Patent Document 2), there is an invention of a metal halide lamp in which a coil is wound around an electrode shaft. This invention is an invention related to a coil design or the like in a mercury-containing lamp, Moreover, there is no description about the arithmetic mean roughness of the electrode shaft which contacts a sealing part. Japanese Patent Application Laid-Open No. 2001-6617 (hereinafter referred to as Patent Document 3) discloses an arc tube invention in which the average roughness of the surface of the tungsten electrode is 3 μm or less. The average roughness of the surface of the electrode shaft is defined when not mounted.

  The present invention has been made in view of the above problems, and an object thereof is to provide a thalhalide lamp capable of suppressing crack leak in a lamp specification in which a coil is wound around an electrode shaft.

  In order to achieve the above object, a 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 enclosed in the discharge space. An essentially mercury-free discharge medium, a proximal end side sealed in the sealing portion, a distal end side sealed in the discharge space, and a pair of electrodes opposed to each other in the discharge space A coil wound around the electrode portion, and the coil is wound so that the sealing portion and the electrode are in contact with each other between the coils. The thickness Ra is 0.20 μm or less.

  According to the present invention, crack leakage can be suppressed in a lamp specification in which a coil is wound around an electrode shaft.

(First embodiment)
Hereinafter, a 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 of the present invention.

  The metal halide lamp has an airtight container 1 as a main part. The airtight container 1 is made of quartz glass having heat resistance and translucency. 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. The volume of the discharge space 14 is 0.1 cc or less for a short arc type discharge lamp, and the volume of the discharge space is 0.01 cc to 0.04 cc when an application is specified for an automobile headlamp. desirable.

  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 sodium, scandium, and zinc halide. Indium and tin halides may be added or substituted. In addition, iodine is most suitable as the halide bonded to these metals, but bromine, chlorine, or a combination of a plurality of halides may be used.

  As the rare gas, xenon which has high luminous efficiency immediately after starting and mainly acts as a starting gas is enclosed. The pressure of xenon is preferably 5 atm or more, more preferably 10 to 15 atm at normal 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 and 3b2 are made of a material mainly containing tungsten, for example, a material obtained by doping tungsten with thorium oxide. The base end side is connected to the end of the metal foils 3a1, 3b1 on the discharge part 11 side by welding, and the other end is kept at a predetermined distance between the electrodes in the discharge space 14 so that the tips of each other face each other. Is arranged. 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.

  The electrodes 3a2, 3b2 are stepped electrodes each having a tip portion 3a21, 3b21 and a shaft portion 3a22, 3b22. The tip portions 3a21, 3b21 are larger in diameter than the shaft portions 3a22, 3b22. The diameter R1 (mm) of the electrode tip is 0.35 mm ≦ R1 ≦ 0.40 mm and is located in the discharge space 14. The diameter R2 of the electrode shaft is 0.30 mm ≦ R2 ≦ 0.35 mm, and is mainly located in the sealing portions 12a and 12b.

  Here, as for axial part 3a22, 3b22, the arithmetic mean roughness Ra is controlled by Ra <= 0.20 micrometer. As a method of reducing the arithmetic average roughness Ra, there is a method of controlling the crystal size of the electrode surface. That is, by heat-treating the electrode at a relatively high temperature, the crystal on the electrode surface is lengthened, the surface is microscopically flattened, and the arithmetic average roughness Ra is reduced. According to this method, the arithmetic average roughness Ra can be reduced to 0.20 μm or less by generating several crystals of 100 μm or more on the surface. The method for controlling the arithmetic average roughness Ra to be small is not limited to the above method, and may be a method by polishing or the like.

  The coils 3a3 and 3b3 are made of, for example, doped tungsten, and are spirally wound around the shaft portions 3a22 and 3b22. The coils 3a3 and 3b3 are formed from the ends of the metal foils 3a1 and 3b1 toward the discharge space 14. The coils 3a3 and 3b3 are preferably wound in a range of 0.55 or more with respect to the electrode length sealed by the sealing portions 12a and 12b.

  FIG. 2 is a view for explaining a cross section of the portion indicated by the alternate long and short dash line X in FIG. 1. As can be seen from the figure, the shaft portion 3a22 is in contact with the sealing portion 12a between adjacent coils of the wound coil 3a3. That is, the shaft portion 3a22 and the sealing portion 12a are not in contact with each other in the gap 15 formed between the coil 3a3, but are in contact with each other. In the present embodiment, the contact length L1 between the shaft portion 3a22 and the sealing portion 12a and the inter-coil distance d are the same length, or L1 is slightly shorter. Further, the gap length L2 of the gap 15 with respect to the shaft portion 3a22 and the coil diameter r are the same length, or L2 is slightly longer. Such a contact state, particularly the length of the contact length L1, can be adjusted by the pinch seal condition.

  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 oxides such as titanium, cerium, and 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.

  These metal halide lamps are arranged with the tube axis in a substantially horizontal state, and by connecting a lighting circuit to the bottom terminal 8a and the side terminal 8b, the stable power is about 35W at the stable time and the stable power at the start time. On the other hand, it is lit at about 75 W, which is twice or more.

  FIG. 3 is a view for explaining one specification of the metal halide lamp of FIG. The following tests are performed based on this specification unless otherwise specified.

Discharge vessel 1: made of quartz glass, volume of discharge space 14 = 0.028 cc, inner diameter A = 2.5 mm, outer diameter B = 6.2 mm, longitudinal sphere length C = 7.8 mm,
Metal halide: ScI ₃ -NaI-ZnI ₂ = 0.6 mg
Noble gas: xenon = 11 atm,
Mercury: 0 mg,
Metal foils 3a1, 3b1: made of molybdenum,
Electrodes 3a2, 3b2: Triated tungsten, tip portions 3a21, 3b21 having diameter R1 = 0.38 mm, shaft portions 3a22, 3b22 having diameter R2 = 0.35 mm, arithmetic average roughness Ra = 0.15 μm, interelectrode distance D = 4.4 mm,
Coils 3a3, 3b3: made of doped tungsten, distance between coils d = 90 μm, coil diameter r = 60 μm, coil pitch P = 250%,
External lead wires 3a4, 3b4: made of molybdenum, diameter = 0.6 mm,
Contact length L1 = 85 μm, gap length L2 = 65 μm, L1 / L2 = 1.30
FIG. 4 is a diagram for explaining the occurrence rate of foil leak when the coil pitch P is changed. In the test, a lighting test was performed with a power of 35 W, and the rate of occurrence of foil leak within 2000 hours is shown. In this test, when the coil pitch P is changed, the gap length L2 hardly changes and only the contact length L1 changes. Further, the coil pitch P is calculated by a calculation formula of P (%) = [(distance between coils d + coil diameter r) / coil diameter r] × 100, and the contact length L1 depends on the coil diameter r and the sealing state. Since the measurement site may vary, the average is obtained by averaging a plurality of points randomly selected from a portion where the coils are regularly arranged.

  From the results, it can be seen that when the coil pitch P is large, the occurrence rate of foil leak is low, and particularly when the coil pitch P is 150% or more (contact length L1 is 30 μm or more), the occurrence rate of foil leak is significantly reduced. Further, it can be seen that when the coil pitch P is 200% or more (contact length L1 is 60 μm or more), foil leakage does not occur.

  The reason for such a result is presumed as follows.

  When the coils 3a3 and 3b3 are wound around the shaft portions 3a22 and 3b22, a gap 15 is generated around the coil as shown in FIG. The gap 15 partially releases the close contact between the electrode shaft and the sealing glass, and thus generates an effect of suppressing shaft leakage and inter-coil leakage. On the other hand, the gap 15 generated when the coils 3a3 and 3b3 are wound serves as a path for the discharge medium in the direction of the metal foils 3a1 and 3b1. Therefore, when the coils 3a3 and 3b3 are tightly wound (for example, 100%), the gap 15 is almost connected, and the discharge medium easily moves between the electrode shaft and the sealing glass. Become. On the other hand, when the coils 3a3 and 3b3 are sparsely wound (for example, 250%), the gap 15 is cut off, and the discharge medium is difficult to move between the electrode shaft and the sealing glass, and foil leakage is caused up to 2000 hours. Can be suppressed. In addition, when the coil pitch P is 150% or more, the rate of occurrence of the foil leakage is remarkably reduced. It is thought that it was because of.

  That is, in order to prevent the intrusion of the discharge medium, it is important that the coils 3a3 and 3b3 are wound so that the electrode shaft and the sealing glass are in contact with each other between the coils. Specifically, the contact length L1 is the most important, and the contact length L1 is preferably 30 μm or more, and preferably the contact length L1 is 60 μm or more. If the contact length L1 is too large, the contact area becomes too large and leakage between coils tends to occur. Therefore, the contact length L1 is preferably within a range of 360 μm or less. Further, in order to more effectively prevent the discharge medium from entering, the relationship between the contact length L1 and the gap length L2 is important, and L1 / L2 is 0.5 or more, preferably L1 / L2 is 1.0. The above is desirable. Note that L1 / L2 is preferably in the range of 6.0 or less.

  FIG. 5 is a diagram for explaining the occurrence rate of cracks when the arithmetic average roughness Ra of the electrode shaft portion is changed. The test is a lighting test with a power of 35 W. Note that the crack in this test refers to a crack that leads to leakage, and specifically, a crack Z1 (shaft portions 3a22, 3b22 having a length twice or more the electrode shaft diameter as shown in FIG. When the diameter R2 is 0.30 mm, it means a crack having a length exceeding 0.6 mm) or a crack Z2 having an angle of 45 ° or more with respect to the electrode surface.

  Here, the measurement site of the arithmetic average roughness Ra is the vicinity of the shaft portions 3a22, 3b22 around which the coils 3a3, 3b3 are wound, for example, the Y point in FIG. In addition, as a measuring device, “Ultra Deep Shape Measuring Microscope VK-8500” manufactured by Keyence Corporation is used, and the value of the arithmetic average roughness Ra is within the surface of the electrode photographed at a magnification of 1000 times with this device. From this, it is a value when a uniform rectangular region of 50 μm × 50 μm is selectively analyzed.

  From the results, the smaller the arithmetic average roughness Ra of the shaft portions 3a22, 3b22, the lower the crack leak rate. In particular, if the arithmetic average roughness Ra is 0.20 μm or less, the crack generation rate is significantly reduced. I understand that. Further, if the arithmetic average roughness Ra is 0.15 μm or less, cracks are not generated.

  From this test, it can be seen that leakage between coils that cannot be suppressed only by the coil design of the test of FIG. 4 can be suppressed by the arithmetic average roughness Ra. That is, in addition to the coil design by the test of FIG. 4, the arithmetic average roughness Ra is 0.20 μm or less, more preferably, the arithmetic average roughness Ra is 0.15 μm or less, so that axial leak, foil leak, and coil It was found that leaks can be suppressed. However, if the arithmetic average roughness Ra is too small, the contact portion is too weak to suppress the intrusion of the discharge medium. Therefore, the arithmetic average roughness Ra is preferably in the range of 0.05 μm or more.

  Therefore, in this embodiment, the coils 3a3 and 3b3 are wound so that the sealing portions 12a and 12b and the shaft portions 3a22 and 3b22 are in contact with each other between the coils. When Ra is 0.20 μm or less, axial leakage, foil leakage, and inter-coil leakage can be suppressed.

  In addition, when the contact length between the sealing portions 12a and 12b and the shaft portions 3a22 and 3b22 between the coils is set to L1, it can be further increased by setting L1 ≧ 60 μm or setting the arithmetic average roughness Ra to 0.15 μm or less. An effect can be obtained.

  The embodiment of the present invention is not limited to the above, and may be modified as follows, for example.

  Since crack probability may occur in the sealing portions 12a and 12b contacting the coils 3a3 and 3b3, although the probability is low, it is desirable to use the one having the smallest possible surface roughness of the coils 3a3 and 3b3.

The whole figure for demonstrating 1st Embodiment of the metal halide lamp of this invention. The figure for demonstrating the cross section of the dashed-dotted line X part of FIG. The figure for demonstrating one specification of the metal halide lamp of FIG. The figure for demonstrating the incidence rate of foil leak when the coil pitch P is changed. The figure for demonstrating the incidence rate of a crack when changing arithmetic mean roughness Ra of an electrode shaft part. The figure for demonstrating the crack which leads to a leak.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Airtight container 11 Discharge part 12a, 12b Sealing part 13a, 13b Non-sealing part 14 Discharge space 15 Crevice 2 Metal halide 2a, 2b Mount 3a1, 3b1 Metal foil 3a2, 3b2 Electrode 3a21, 3a22 Tip part 3a22, 3a22 Axis 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 (4)

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, an essentially mercury-free discharge medium enclosed in the discharge space, and a base end The side is sealed in the sealing part, and the tip side is provided with a pair of electrodes arranged opposite to each other in the discharge space, and a coil wound around the electrode part sealed in the sealing part. ,
The coil is wound so that the sealing portion and the electrode are in contact with each other between the coils, and the electrode has an arithmetic average roughness Ra of 0.20 μm or less. .   2. The metal halide lamp according to claim 1, wherein L <b> 1 is 30 μm or more, where L <b> 1 is a contact length between the sealing portion and the electrode between the coils.   The relation L1 / L2 between the contact length L1 and the gap length L2 is 0.5 or more, where L2 is a gap length due to a gap generated between the coil and the electrode. Item 3. A metal halide lamp according to Item 2. 4. The metal halide lamp according to claim 1, wherein the electrode has an arithmetic average roughness Ra of 0.15 μm or less. 5.

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