JP6662203B2 - Discharge lamp - Google Patents

Description

  The present invention relates to a discharge lamp.

  In a discharge lamp such as a metal halide lamp used for a wide range of illumination or the like, cracks may be generated in the arc tube due to thermal strain.

  Conventionally, in order to suppress the occurrence of cracks, the distance from the connection between the glass tube of the arc tube body and the glass tube of the sealing portion to the tip of the electrode mount is X, and the distance from the connection to the tip of the glass beads is X. When the distance is defined as Y, a discharge lamp is known in which X falls within a range of 5 to 15 mm and Y falls within a range of 0.5 to 2.0 mm (for example, see Patent Document 1).

JP-A-2005-185261

  However, even in the above-described discharge lamps, it is a fact that thermal strain is inevitably accumulated in the arc tube, and a discharge lamp that does not accumulate thermal strain as much as possible is desired.

  The present invention has been made to solve the above problem, and has as its object to provide a discharge lamp capable of suppressing thermal distortion accumulated in an arc tube.

  A discharge lamp according to one embodiment of the present invention includes an arc tube, a discharge space surrounded by the arc tube, and an electrode whose electrode core is sealed at an end of the arc tube. And a narrow shaft portion that is continuous with the main body portion and has a smaller cross-sectional area as viewed from the axial direction than the main body portion. The discharge shaft side end of the sealing portion of the electrode core to the arc tube is the fine shaft portion. It is.

  A discharge lamp capable of suppressing thermal distortion accumulated in an arc tube can be provided.

It is a conceptual diagram showing the composition of discharge lamp 1 concerning this embodiment. FIG. 2 is a conceptual diagram showing an enlarged cross-sectional configuration of one end of the discharge lamp 1 of FIG. 1. 5 is a graph showing the temperature of each part of the electrode 40 during light emission in the discharge lamp 1 according to the embodiment. FIG. 2 is a conceptual diagram showing a configuration of an electrode 40 provided in the discharge lamp 1 of FIG. 1 when viewed in a Y-axis direction. FIG. 5 is a conceptual diagram showing the electrode 40 of FIG. 4 when viewed in the Z-axis direction. It is a conceptual diagram which shows the structure of the electrode 40A which concerns on a modification seen from the Y-axis direction.

  Hereinafter, a discharge lamp according to an embodiment of the present invention will be described with reference to the drawings. Each of the embodiments described below shows a preferred specific example of the present invention. Numerical values, shapes, materials, constituent elements, arrangement positions of constituent elements, connection forms, and the like shown in the following embodiments are merely examples, and do not limit the present invention. In addition, among the components in the following embodiments, components not described in the independent claims indicating the highest concept are described as arbitrary components. Further, the following drawings are schematic diagrams, and are not necessarily strictly illustrated.

  The present inventor has found that when the periphery of the electrode on the inner surface of the arc tube is close to the tip (pole head) of the electrode, heat from the tip easily transfers to the sealing portion of the arc tube, and It has been found that thermal strain accumulates in the sealing portion.

  For this reason, the present inventor first increases the total length of the electrode core having the same width as a whole, so that the sealing portion of the arc tube and the tip of the electrode are separated from each other, and the sealing portion of the arc tube is separated from the electrode. Reduction of heat transfer was studied. However, in this case, the distance between the end portion in the arc tube (the coldest portion in the arc tube) and the tip of the electrode increases, and the temperature of the coldest portion becomes excessively low. It is not desirable to lower the temperature of the coldest part, because blackening of the discharge lamp proceeds.

  Next, the inventor of the present invention diligently studied a technique capable of suppressing both the blackening of the discharge lamp and the accumulation of thermal strain in the arc tube. Accordingly, the inventor of the present invention has a configuration in which the electrode core is provided with the main body and the narrow shaft portion having a smaller cross-sectional area than the main body, and the end of the electrode core on the discharge space side in the sealing portion to the arc tube. Is focused on the point that is a thin shaft portion. Since the thin shaft portion has a smaller cross-sectional area than the main body portion, the thermal conductivity increases and the temperature decreases. Thereby, the heat transmitted from the thin shaft portion to the arc tube can be reduced, and the thermal strain accumulated in the arc tube is suppressed. Further, when the thin shaft portion of the electrode core is sealed in the arc tube, it is not necessary to lengthen the electrode core itself. For this reason, the tip portion of the electrode and the coolest portion come closer to each other, and it is possible to suppress a decrease in the temperature of the coolest portion. Therefore, blackening of the discharge lamp can be suppressed.

  Therefore, the present inventor has found that this configuration can suppress both blackening of the arc tube and thermal strain accumulated in the arc tube.

  FIG. 1 is a conceptual diagram showing a configuration of a discharge lamp 1 according to the present embodiment. FIG. 2 is a conceptual diagram showing an enlarged sectional configuration of one end of the discharge lamp 1 of FIG.

  The discharge lamp 1 is, for example, a so-called metal halide lamp in which a metal halide (metal halide) is added to high-pressure mercury vapor and light emission by arc discharge of the metal halide is used.

  Specifically, as shown in FIGS. 1 and 2, the discharge lamp 1 includes a light emitting tube 10, a discharge space 20 surrounded by the light emitting tube 10, and an electrode core 41 sealed at the end 12 of the light emitting tube 10. And a stopped electrode 40. The electrode core 41 of the electrode 40 includes a main body 411 and a thin shaft 412 that is continuous with the main body 411 and has a smaller cross-sectional area than the main body 411 in the axial direction (X-axis direction). An end of the electrode core 41 on the discharge space 20 side in the sealing portion 60 to the arc tube 10 is a thin shaft portion 412. The thin shaft portion 412 is sealed to the end of the arc tube 10 with the boundary 413 between the main body 411 and the thin shaft portion 412 exposed from the inner surface of the arc tube 10.

  FIG. 3 is a graph showing the temperature of each part of the electrode 40 at the time of light emission in the discharge lamp 1 according to the present embodiment. In FIG. 3, a temperature change corresponding to the electrode 40 according to the present embodiment is indicated by a solid line L1, and a temperature change of an electrode (comparative example) having an electrode core having a uniform cross-sectional area as a whole is indicated by a broken line L2. . Also, in FIG. 3, the electrodes 40 are illustrated in order to clarify the correspondence between the respective positions of the electrodes 40.

  As shown by the broken line L2, in the case of the comparative example, the temperature change gradually decreases as the distance from the tip of the electrode core increases. On the other hand, in the case of the electrode 40 of the present embodiment, it can be seen that the temperature suddenly drops from the boundary 413, and the temperature of the thin shaft portion 412 is lower than in the comparative example.

  As described above, in the discharge lamp 1 according to the present embodiment, the boundary 413 between the main body portion 411 and the thin shaft portion 412 in the electrode core 41 is exposed from the inner surface of the arc tube 10. Heat will be transferred to 10. Since the narrow shaft portion 412 has a smaller cross-sectional area than the main body portion 411, the thermal conductivity increases, and the temperature decreases. Thereby, heat transmitted from the thin shaft portion 412 to the arc tube 10 can be reduced, and thermal strain accumulated in the arc tube 10 can be suppressed.

  In addition, when the thin shaft portion 412 of the electrode core 41 is sealed in the arc tube 10, the effect of suppressing thermal distortion can be obtained without increasing the length of the electrode core 41 itself. For this reason, the tip portion of the electrode core 41 and the coldest portion come closer to each other, and it is possible to suppress a decrease in the temperature of the coldest portion. Therefore, blackening of the discharge lamp 1 can be suppressed.

  Here, the arc tube 10 has a cylindrical main body 11 and a cylindrical end 12 having an opening area smaller than that of the main body 11. The main body 11 has a cylindrical shape and is elongated in the X-axis direction, and an intermediate portion 13 and an end 12 are provided at both ends of the main body 11, respectively. Further, each end portion 12 has a cylindrical shape, and each intermediate portion 13 has a curved (arc-shaped) outer shape in a cross section (for example, a cross section in the XZ plane). Further, on the end side 12 of the arc tube 10, for example, an infrared reflection film (heat insulation film) made of a gold film or a silica film may be formed over the entire circumference. Further, bases 30 are attached to both ends of the arc tube 10.

  Each of the ends 12 of the arc tube 10 is provided with a sealing portion 60 for sealing one end of the electrode core 41. The sealing portion 60 is a quartz bead (insertion tube) separate from the arc tube 10 before sealing. The sealing portion 60 is melted by being heated at the time of sealing, and is integrated with the arc tube 10 to become a part of the arc tube 10. For this reason, after sealing, the boundary of the sealing portion 60 (broken line L shown in FIG. 2) may partially remain, or may disappear entirely. The portion of the electrode core 41 that is sealed by the sealing portion 60 is the thin shaft portion 412 throughout. Further, the sealing portion 60 may or may not protrude inward from the end portion 12 of the arc tube 10 as shown in FIG.

  FIG. 4 is a conceptual diagram showing the configuration of the electrode 40 provided in the discharge lamp 1 of FIG. 1 when viewed in the Y-axis direction. FIG. 5 is a conceptual diagram showing the electrode 40 of FIG. 4 when viewed in the Z-axis direction.

  As shown in FIGS. 4 and 5, each of the pair of electrodes 40 has an electrode core 41 and a coil 42. The electrode core 41 is a rod-shaped body made of a heat-resistant metal such as tungsten. The main body 411 of the electrode core 41 is formed in a cylindrical shape, and the coil 42 is wound therearound. The coil 42 is a coil body wound around the main body 411 of the electrode core 41, and is made of a heat-resistant metal such as tungsten.

  The thin shaft portion 412 of the electrode core 41 includes a connecting portion 414 connected to the main body portion 411, and a long portion 415 extending continuously from the connecting portion 414. The connecting portion 414 is an end of the thin shaft portion 412 on the main body 411 side. The connecting portion 414 has a shape that tapers toward the base end side of the electrode core 41, and the entire peripheral surface thereof is concavely curved.

  As described above, since the connecting portion 414 is curved in a concave shape, the sectional area does not change abruptly from the main body portion 411 to the thin shaft portion 412. Therefore, the stress concentrated at the boundary 413 between the main body 411 and the thin shaft 412 can be reduced, and the strength of the electrode core 41 itself can be suppressed from being reduced.

  The thin shaft portion 412 is sealed in the arc tube 10 from a concavely curved portion (connecting portion 414).

  As described above, since the thin shaft portion 412 is sealed in the arc tube 10 from the connecting portion 414, the electrode core 41 can be sealed with the arc tube 10 at a portion where the cross-sectional area changes, and stable strength is obtained. Can be secured.

  Specifically, the long section 415 has a rectangular cross-sectional shape when viewed from the axial direction. The long portion 415 has a uniform thickness (length in the Z-axis direction) as a whole as shown in FIG. 4, but has a width (length in the Y-axis direction) at the base end as shown in FIG. The shape is gradually tapered toward. As described above, since the thin shaft portion 412 is gradually tapered, the cross-sectional area becomes smaller as the distance from the main body portion 411 increases. That is, since the thermal conductivity increases as the distance from the main body 411 increases, the temperature of the thin shaft 412 can be further reduced. Note that the ratio of the cross-sectional area of the long portion 415 to the cross-sectional area of the main body 411 is preferably 0.90 or less.

Further, mercury for a buffer gas, iron as a main luminescent metal, iodine and bromine as halogens, and a rare gas for starting are further sealed in the arc tube 10. Halogen can be sealed in the arc tube 10 in the form of a metal halide such as FeI ₂ , FeBr ₂ , HgI ₂ , HgBr ₂ , and mercury and iron can be sealed as a metal halide or a metal alone, and these can be combined as appropriate. And sealed in a predetermined amount and ratio. Preferably, a metal halide containing bromine is used as the halogen. Further, He, Ne, Xe, Ar, Kr, or the like can be used as the rare gas.

  As described above, the temperature of the electrode 40 tends to increase when a bromine-based filling material is used, such as when a metal halide containing bromine is used as a halogen. From the heat to the arc tube 10 can be reduced, and accumulation of thermal strain can be suppressed.

  In the above embodiment, the case where the thin shaft portion 412 has the connecting portion 414 and the long portion 415 has been described as an example, but the connecting portion 414 may not be provided. Hereinafter, the thin shaft portion 412a having no connecting portion will be described with reference to FIG. In the following description, the same parts as those in the above embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

  FIG. 6 is a conceptual diagram showing the configuration of an electrode 40A according to a modification as viewed in the Y-axis direction. Specifically, FIG. 6 is a diagram corresponding to FIG. As shown in FIG. 6, the thin shaft portion 412a according to the modified example has no connecting portion and the long portion 415 is directly connected to the main body portion 411. As a result, the boundary between the main body 411 and the thin shaft 412a has a stepped shape.

  Further, in the above-described embodiment, the case where the cross-sectional shape of the long portion 415 viewed from the axial direction is rectangular is illustrated, but the cross-sectional shape of the long portion 415 may be any shape. Other cross-sectional shapes include, for example, polygonal shapes other than rectangles, circular shapes, elliptical shapes, oval shapes, and the like.

  In the above-described embodiment, the intermediate portion 13 has a curved (arc-shaped) outer shape in a cross section (for example, a cross section in the XZ plane). However, the intermediate portion 13 has a linear or polygonal outer shape in the cross section. May be provided.

DESCRIPTION OF SYMBOLS 1 Discharge lamp 10 Arc tube 11 Main part 12 End part 13 Intermediate part 20 Discharge space 30 Base 40, 40A Electrode 41 Electrode core 42 Coil 60 Sealing part 411 Main part 412, 412a Thin shaft part 413 Boundary 414 Connecting part 415 Long Department

Claims (4)

An arc tube,
A discharge space surrounded by the arc tube;
An electrode whose electrode core is sealed at an end of the arc tube,
The electrode core includes a main body, and a thin shaft portion that is continuous with the main body and has a smaller cross-sectional area as viewed from the axial direction than the main body,
Ri the discharge space side of the end portion is the thin shaft der in the sealing portion to the arc tube of the electrode core,
An end portion of the thin shaft portion on the main body portion side is curved in a concave shape,
The discharge lamp in which the narrow shaft portion is sealed in the arc tube from the middle of the concavely curved portion . The discharge lamp according to claim 1, wherein the thin shaft portion is sealed to the end of the arc tube in a state where a boundary between the main body and the thin shaft portion is exposed from an inner surface of the arc tube. 3. The discharge lamp according to claim 1, wherein a portion of the electrode core that is sealed at an end of the arc tube is the thin shaft portion as a whole. 4. Wherein the arc tube, the discharge lamp according to any one of claims 1 to 3, a metal halide containing bromine is sealed as a halogen.

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