JP2009123415A - Discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp capable of suppressing axial leak. <P>SOLUTION: This discharge lamp is equipped with an airtight vessel 1 having a discharge part 11 in which a discharge space 14 is formed, sealing parts 12a, 12b formed at the ends of the discharge part 11, a discharge medium filled in the discharge space 14, and a coil-wound electrode 32 in which a coil 322 is wound around the axis of an electrode 321, with the ends sealed in the sealing parts 12a, 12b together with the coil 322. Cracks 9 are formed in the sealing parts 12a, 12b along the almost axial direction of the electrode with the surface of the coil 322 as a starting point. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a discharge lamp used for an automotive headlamp, a liquid crystal projector, and the like.

  A discharge lamp used for an application such as an automobile headlamp is known from, for example, Japanese Patent Application Laid-Open No. 2005-339999 (hereinafter referred to as Patent Document 1), and a discharge portion in which a discharge space is formed and both ends thereof. The one end side of the electrode is opposed to the inside, and the other end side is sealed to the sealing portion of the electrode. Since such a discharge lamp is often lit at a relatively high load, a crack is likely to occur in the sealing portion where the electrode is sealed when the lamp is lit, and a malfunction (hereinafter referred to as an axial leak) is likely to occur. It is known. Therefore, as a countermeasure against this shaft leak, a configuration is adopted in which a coil is wound around the electrode shaft portion sealed in the sealing portion.

JP 2005-339999 A

  However, when the coil is wound around the electrode, the occurrence rate of the shaft leak is certainly reduced, but it cannot be completely prevented, and in some cases, the shaft leak may occur in a relatively short period of time. For this reason, it is necessary to further improve the reliability with respect to the suppression of shaft leakage.

  An object of the present invention is to provide a discharge lamp capable of suppressing axial leakage.

  In order to achieve the above object, a discharge lamp of the present invention is sealed in an airtight container having a discharge part in which a discharge space is formed, a sealing part formed at an end of the discharge part, and the discharge space. In the discharge lamp comprising a discharge medium having a coil wound around an electrode shaft and one end sealed in the sealing portion together with the coil, the sealing portion includes the A crack is formed substantially along the electrode axis direction starting from the surface of the coil.

  According to the present invention, shaft leakage can be suppressed.

(First embodiment)
Hereinafter, a metal halide lamp used as a discharge lamp for an automobile headlamp will be described as an example with reference to the drawings. FIG. 1 is a view for explaining a first embodiment of a metal halide lamp of the present invention.

  In the metal halide lamp, the hermetic container 1 is formed of a material having heat resistance and translucency, for example, quartz glass. 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 desirably at 100 mm ³ or less, when used as vehicle ^headlights, is preferably a 10mm ³ ~40mm 3.

  A discharge medium is sealed in the discharge space 14. As the discharge medium, a metal halide 2 and a rare gas are enclosed. The metal halide 2 is composed of sodium halide, scandium halide, zinc halide, and indium halide. As the halogen, iodide or bromide is desirable. In addition, the rare gas has high luminous efficiency immediately after starting, and xenon (Xe), which mainly acts as the starting gas, is enclosed at a pressure of 5 atm or higher, preferably 10 atm or higher at room temperature (25 ° C.).

  Here, the discharge space 14 does not contain substantial mercury. This “substantially free of mercury” means an amount equivalent to no mercury or almost not enclosed even when compared with a conventional mercury-containing metal halide lamp, for example, less than 2 mg per ml, preferably This means that even if an amount of mercury of 1 mg or less is present, it is acceptable.

  Note that the metal and halogen of the metal halide 2, the kind and combination of rare gas, and the presence or absence of mercury are not limited to the above, and various changes can be made.

  The electrode mount 3 is sealed inside the sealing portions 12a and 12b. The electrode mount 3 includes a metal foil 31, a coil winding electrode 32, and a lead wire 33.

  The metal foil 31 is a thin metal plate made of, for example, molybdenum.

  The coil winding electrode 32 further includes an electrode 321 and a coil 322.

  The electrode 321 is a triated tungsten electrode in which tungsten is doped with thorium oxide. The base end side is connected to the end portion of the metal foil 31 on the discharge portion 11 side by laser welding, and the tip end side is arranged so that the tip ends thereof are opposed to each other while maintaining a predetermined distance between the electrodes in the discharge space 14. Has been. Here, the predetermined inter-electrode distance is 5 mm or less in terms of appearance, and 4.1 mm to 4.5 mm (3.5 mm to 3.9 mm in actual distance) when used for automobile headlamps. It is desirable.

  The coil 322 is made of, for example, doped tungsten, and is wound spirally around the axis of the shaft portion of the electrode 321 sealed to the sealing portions 12a and 12b. However, the coil 322 is not wound around the shaft portion of the electrode 321 connected to the metal foil 31, but is wound in the direction of the discharge space 14 from the end of the foil.

  The lead wire 33 is made of, for example, molybdenum, and is connected to the end portion of the metal foil 31 on the opposite side to the discharge portion 11 by laser welding. The other end of the lead wire 33 extends outside the sealing portions 12a and 12b along the tube axis. Note that one end of an L-shaped support wire 34 made of nickel is connected to the lead wire 33 extending to the front end side. The other end of the support wire 34 extends in the direction of a socket 6 described later, and a sleeve 4 made of ceramic is coated on a portion parallel to the tube axis.

  On the outside of the hermetic container 1 configured as described above, a cylindrical outer tube 5 made by adding an oxide such as titanium, cerium, or aluminum to quartz glass is substantially concentric with the hermetic container 1 along the tube axis. Is provided. 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. In the space between the airtight container 1 and the outer tube 5, for example, a rare gas such as nitrogen, neon, argon, xenon, or the like can be mixed or sealed at a pressure of 0.05 atm to 0.3 atm.

  And the socket 6 is connected to the non-sealing part 13a side of the outer tube 5 in a state of covering the airtight container 1 inside. For these connections, the metal band 71 attached to the outer peripheral surface of the outer tube 5 in the vicinity of the non-sealed portion 13a is connected to 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). In order to further strengthen the connection, the contact points of the metal band 71 and the tongue piece 72 are welded by laser. A bottom terminal 8a and a side terminal 8b are formed at the bottom of the socket 6, and a lead wire 33 and a support wire 34 are connected to the socket 6, respectively.

  The lamp composed of these is arranged so that the tube axis is horizontal, and a lighting circuit (not shown) is connected to the bottom terminal 8a and the side terminal 8b. It is lit by turning on about 75W and about 35W when stable.

  Here, the coil winding electrode 32 will be described in detail with reference to FIGS. 2 and 3. FIG. 2 is an enlarged view for explaining a range surrounded by a one-dot chain line X in FIG. 1, and FIG. 3 is a cross-sectional view of substantially the same range.

  As can be seen, cracks 9 are formed in the sealing portion 12a. The crack 9 starts from the vicinity of the top of the coil 322 and extends substantially along the electrode axis direction and is connected to the adjacent coil 322. Thereby, generation | occurrence | production of an axial leak can be suppressed effectively. Of course, it is desirable that the crack 9 be formed not only on one sealing portion but also on the other sealing portion 12b. Here, “substantially electrode axis direction” means that the angle α of the crack 9 with respect to the electrode axis direction is ± 45 ° or less, preferably ± 20 ° or less.

  Next, a method for forming the crack 9 will be described.

  First, a coil 322 formed in a spiral shape on the shaft of the electrode 321 is attached and fixed in advance to form the coil winding electrode 32. At this time, when the diameter R of the electrode 321 is about 0.30 mm to 0.40 mm, the coil 322 preferably has a diameter r of 0.050 mm or more and a pitch P of 300% or less.

  Next, the coil winding electrode 32 is put into a heating furnace to perform heat treatment. This process is a process performed for the purpose of releasing impure gas contained in the metal material. In this step, care must be taken to heat the coil winding electrode 32 at a temperature at which the surface of the coil 322 is crystallized long, for example, the crystal does not become larger than 0.005 mm.

  And the coil winding electrode 32 obtained through such a process, the metal foil 31, and the lead wire 33 are joined and the electrode mount 3 is formed, Then, it seals by the well-known method to the sealing part 12a. Thereby, perhaps, while the sealing portion 12a cools from high temperature to room temperature, the crack 9 extending substantially along the electrode axis direction can be formed in the sealing portion 12a starting from the vicinity of the surface of the coil 322.

FIG. 4 is a view for explaining an embodiment of the metal halide lamp of FIG. The following tests are performed based on this specification unless otherwise specified.
(Example)
Discharge vessel 1; made of quartz glass, inner volume of discharge space 14 = 27 mm ³ , inner diameter A = 2.5 mm, outer diameter B = 6.2 mm, spherical length C in the longitudinal direction C = 7.8 mm,
Metal halide _{2; ScI 3 -NaI-ZnI 2} -InBr = 0.30mg
Noble gas; xenon = 10 atm,
Mercury; 0 mg,
Metal foil 31; made of molybdenum,
Electrode 321; Triated tungsten, diameter R = 0.33 mm, distance between electrodes D = 3.75 mm,
Coil 322; made of doped tungsten, diameter r = 0.09 mm, coil pitch P = 200%, surface is composed of fine crystals (= no long crystal),
Crack 9: A crack as shown in FIG. 2 is formed over almost the entire coil winding length.

  When the lamp of this example was lit for 2500 hours under the lighting condition of the blinking cycle of the EU120 minute mode defined in JEL215, which is the standard of the automotive headlamp HID light source, no shaft leak occurred for 15 of 15 lamps. It was confirmed that the life characteristics were good. This is because the crack 9 starts from a sealing glass portion that is in contact with the axis of the electrode 321 causing the axial leakage, and a vertical crack (hereinafter referred to as a vertical crack) progresses in the thickness direction of the sealing portions 12a and 12b. It is presumed that this was prevented. That is, since the crack 9 is a crack in a direction substantially perpendicular to the vertical crack, it is considered that even if the vertical crack occurs, the crack 9 stops at the crack 9 and the vertical crack does not progress any further. Further, since the crack 9 has the upper half such as the vicinity of the top of the coil 322 as a base point, even if a vertical crack occurs starting from the coil 322, the crack leak can be similarly suppressed.

  Here, the present inventor has clarified the mechanism by which the crack 9 occurs in the sealing portions 12a and 12b. As a result, it has been found that the ease of formation of the crack 9 as in the present invention is influenced by the surface state of the coil.

  5 is a diagram for explaining a range surrounded by a two-dot chain line Y in FIG. 3, FIG. 6 is a diagram for explaining a cross section perpendicular to the tube axis direction, and FIG. Lamp (b) is a conventional lamp. FIG. 5 can be obtained by polishing the sealing portions 12a and 12b sealing the coil winding electrodes 32 and 3b2 along the tube axis direction, and FIG. 6 can be obtained by polishing them perpendicularly to the tube axis direction.

  As can be seen from FIG. 6A, the cross section of the coil 322 is constituted by the speckled fine crystal part 3221. In FIG. 5B, although a part is the fine crystal part 3221, more than half is smooth. It is composed of a long crystal part 3222. That the cross section is constituted by the fine crystal part 3221 as in (a) means that the surface is in a rough state. On the other hand, the fact that the cross section is constituted by the long crystal part 3222 as shown in (b) is a result of the fact that the crystal part 3221 was originally a fine crystal part 3221 but partly bonded by heat to form a long crystal. , Which means that the surface is in a smooth state. That is, in (a), the coil surface and the glass are easily meshed, and in (b), it is difficult to mesh, so when the coil winding electrode 32 expands and contracts due to heat, the crack 9 occurred in (a), but in (b) It is estimated that it did not occur.

  Therefore, the formation state of the crack 9 was observed by changing the crystal state of the coil surface. The result is shown in FIG. The crystal state of the surface is expressed in the range of a long crystal on the outer surface of the coil (= the coil surface on the non-contact side with the electrode) and is calculated from the cross section as shown in FIG. The crystal state was changed by adjusting conditions such as heating temperature and heating time in the heat treatment step.

  As can be seen from the results, the smaller the proportion of long crystals on the outer surface in contact with the sealing portion, the easier the crack 9 is formed. The crack generation rate is 90% at 20% or less, and the crack generation rate is 100 at 10% or less. %. Therefore, in order to form the crack 9, it is desirable that the range of the long crystal on the outer surface of the coil is 20% or less, more preferably 10% or less, and optimally no long crystal exists.

  The axial length L between the coils of the crack 9 needs to be a certain length in order to prevent the progress of the vertical crack. According to the inventor's test, as shown in FIG. 8, even when the coil is formed only halfway, the inter-coil axial length L is 50% or more of the inter-coil distance d. 2 is preferable, and it is optimal if the adjacent coils 322 are connected as shown in FIG. 2 (the inter-coil axial length L is almost 100% with respect to the inter-coil distance d). It was. Further, as a result of the examination, it was found that the axial length L of the crack 9 changes depending on the pitch P and the diameter r of the coil 322.

  FIG. 9 is a diagram for explaining a crack formation state when the pitch P and the diameter r of the coil are changed. In the figure, x indicates that the axial length L is less than 50% with respect to the inter-coil distance d, and ○ indicates that the inter-coil axial length L is 50% or more with respect to the inter-coil distance d. ◎ indicates the state where the crack 9 is connected between the coils.

  As can be seen from the results, the smaller the coil pitch P, the more the crack 9 having a longer inter-coil axial length L with respect to the inter-coil distance d tends to be formed. A crack 9 having a long direction length L is obtained, and if it is 200% or less, the crack 9 connected between the coils can be obtained with high probability. Therefore, the pitch P is preferably 300% or less, more preferably 200% or less, and optimally the lower limit is the pitch P = 100%.

  It can also be seen that a larger coil diameter r is desirable. This is because if the diameter r of the coil is large, the expansion and contraction of the coil is increased, and the glass is easily cracked 9. According to FIG. 9, when the diameter r of the coil is 0.050 mm or more, and further 0.080 mm or more, it was confirmed that the crack 9 is easily formed and is easily connected between the coils. However, the diameter r is preferably 0.150 mm or less because the contact strength between the electrode and glass is too low.

  As described above, whether or not the crack 9 is formed by the crystal state of the coil first, the pitch P second, and the coil diameter r third, depends on the sealing conditions of the sealing portions 12a and 12b. Since it is somewhat affected by (temperature and pressure at the time of sealing) and the like, it is desirable to adjust appropriately.

  Therefore, in the present embodiment, the vertical cracks that cause axial leakage from the electrode shaft 321 are formed in the sealing portions 12a and 12b by forming the cracks 9 substantially along the electrode axis direction starting from the surface of the coil 322. Even if this occurs, the progress can be stopped, so that the occurrence of shaft leakage can be suppressed.

  In addition, the reproducibility of the crack 9 is achieved by setting the ratio of long crystals on the outer surface of the coil 322 that contacts the sealing portions 12a and 12b to 20% or less, the pitch P to 300% or less, and the diameter r to 0.050 mm or more. Can be increased.

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

  The crack 9 is preferably formed in the entire coil 322 as shown in FIG. 2, but it is not always necessary to be formed in the entire length of the coil, and if it is formed in a portion where axial leakage is likely to occur. Good. The “part where the axial leak is likely to occur” indicates a boundary part between the compressive strain and the tensile strain generated in the sealed coil winding electrode 32. Note that the boundary between compressive strain and tensile strain can be confirmed by a sensitive color plate method (a method for identifying the state of strain generated in glass by the optical path difference of light). The vicinity of 1/3 point from the 11 side corresponds to this part.

  Further, the crack 9 may be generated starting from the lower half of the coil 322 as shown in FIG. 10, and in this case as well, the occurrence of axial leakage can be suppressed.

  Further, instead of the crystal state of the coil 322, the contact between the coil and the glass may be strengthened by roughening the surface, and the crack 9 may be generated. In that case, the average surface roughness Ra of the coil 322 is preferably 0.00001 mm or more and 0.001 mm or less as measured by a contact microscope.

The figure for demonstrating 1st Embodiment of the metal halide lamp of this invention. The enlarged view for demonstrating the range enclosed with the dashed-dotted line X of FIG. Sectional drawing for demonstrating the range enclosed by the dashed-dotted line X of FIG. The figure for demonstrating one Example of the metal halide lamp of FIG. The figure for demonstrating the range enclosed by the dashed-two dotted line Y of FIG. The figure for demonstrating the formation state of a crack when changing the crystal state of a coil. The figure for demonstrating the crack generation rate when the ratio of the long crystal | crystallization on the outer surface which contacts a sealing part is changed. The figure for demonstrating the modification 1 of this invention. The figure for demonstrating the formation state of a crack when the pitch P and the diameter r of a coil are changed. The figure for demonstrating the modification 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Airtight container 11 Discharge part 12a, 12b Sealing part 13a, 13b Non-sealing part 14 Discharge space 2 Metal halide 3 Electrode mount 31 Metal foil 32 Coil winding electrode 321 Electrode 322 Coil 33 Lead wire 34 Support wire 4 Sleeve 5 Outer tube 6 Socket 71 Metal band 72 Tongue piece 8a Bottom terminal 8b Side terminal 9 Crack

Claims (5)

An airtight container having a discharge part in which a discharge space is formed, a sealing part formed at the end of the discharge part, a discharge medium sealed in the discharge space, and a coil is wound around the electrode shaft In a discharge lamp comprising a coil-wound electrode with one end sealed in the sealing portion together with the coil,
The discharge lamp according to claim 1, wherein a crack is formed in the sealing portion substantially along the electrode axis direction starting from the surface of the coil.   2. The discharge lamp according to claim 1, wherein the coil has a ratio of long crystals of 20% or less on an outer surface in contact with the sealing portion.   The discharge lamp according to claim 1 or 2, wherein a pitch P of the coil is 300% or less.   The discharge lamp according to any one of claims 1 to 3, wherein the coil has a diameter r of 0.050 mm or more.   A coil-wound electrode on which a coil having a length of a large crystal on the outer surface of 20% or less, a pitch P of 300% or less and a diameter r of 0.050 mm or more is wound is sealed to a sealing portion, and the sealing A discharge lamp characterized in that a crack is formed in a portion along a substantially electrode axis direction starting from the surface of the coil.

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