JP2010113881A - Discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an electrode shaft part from bending through prevention of its excessive temperature rise caused by heat of a coil part highly heated at startup of a discharge lamp directly transmitted to the electrode shaft part. <P>SOLUTION: Of the discharge lamp provided with an arc tube, sealing parts formed at either end of the arc tube, a pair of electrodes held by the sealing parts and arranged in opposition separated from each other inside the arc tube, and coil parts mounted on the electrodes so as to be extended along a center axis of the electrodes, each electrode is structured of an electrode shaft part and an electrode body part integrally formed at a tip of the former and thicker than the same, and each coil part is arranged so as to surround side faces of the electrode shaft part while being separated from the same, fixed only to the same. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a short arc type discharge lamp. For example, the present invention relates to a short arc type discharge lamp which is a light source for a projector device such as a liquid crystal display device or a DLP (digital light processor) using a DMD (digital mirror device).

  Projection light sources such as data projectors are required to have high illuminance, high luminance, and high color rendering, and the light source itself is desired to be miniaturized. In order to meet these demands, as a light source for a data projector, a short arc type discharge lamp in which mercury is sealed in an arc tube or various light emitting metal halides are applied.

FIG. 9 shows the overall configuration of a conventional discharge lamp, and FIG. 10 is a cross-sectional view of electrodes in the discharge lamp of FIG.
The discharge lamp includes an arc tube 90, sealing portions 91 and 92, electrodes 93 and 94, coil portions 95 and 96, metal foils 97 and 98, and external conductors 99 and 100. The arc tube 90 and the sealing portions 91 and 92 are made of quartz glass, the electrodes 93 and 94 are made of tungsten, the coil portions 95 and 96 are made of tungsten, the metal foils 97 and 98 are made of molybdenum foil, and the external conductors 99 and 100 are made of tungsten. Molybdenum is used. In the arc tube 90, a light emitting metal such as mercury or a metal halide is sealed as a discharge medium, and a rare gas such as argon is sealed in order to improve startability.

  In the above discharge lamp, when a predetermined voltage is applied between the external conductors 99 and 100, an arc discharge is generated between the pair of electrodes 93 and 94, and light emission specific to mercury or metal halide is obtained. This type of discharge lamp has a very short distance between electrodes, and a large current flows at start-up. Therefore, it is easy to cause electrode deformation and blackening of the arc tube due to evaporation of electrode constituent materials, and it is difficult to extend the life. . In contrast, attempts have been made to improve lamp life by improving the electrode structure.

  For example, the discharge lamp disclosed in Patent Document 1 includes an electrode 93 including an electrode shaft portion 931 and a discharge portion 932 having a diameter larger than that and formed integrally with the electrode shaft portion 931. . The electrode 93 is easily formed by cutting out a cylindrical electrode material. A coil is mounted behind the discharge portion 932 so as to surround the electrode shaft portion 931. The coil 95 is made of pure tungsten, and is fixed to the electrode shaft portion 931 by spot welding or the like, for example. Similarly to the electrode 93, the electrode 94 includes an electrode shaft portion 941 and a discharge portion 942.

  According to the technique described in the same document, since the heat capacity of the large-diameter discharge part 932 is large and the heat conductivity of the discharge part 932 is good, even if a relatively large current flows, the electrode 93 is excessively heated. There is an effect to suppress. Further, the coil 95 is supposed to have an effect of increasing heat dissipation of the electrode shaft portion 931 to suppress excessive temperature rise and preventing the electrode shaft portion 931 from being thinned or broken.

JP 2000-231903

  In this type of short arc type discharge lamp, the coil portions 95 and 96 are heated by glow discharge and the temperature of the coil portions 95 and 96 is rapidly increased at the time of start-up. Transition. However, in the electrode of FIG. 10, the heat of the coil portions 95 and 96 heated to the high temperature by the glow discharge and the arc discharge is directly transmitted to the electrode shaft portions 931 and 941, and the temperature of the electrode shaft portions 931 and 941 is increased. There is a problem in that the electrode shaft portions 931 and 941 are bent by being excessively raised.

  The present invention has been made in view of the circumstances as described above. The purpose of the present invention is to directly transfer the heat of the coil portion, which has become a high temperature at the start of the discharge lamp, to the electrode shaft portion, so that the temperature of the electrode shaft portion can be improved. It is to prevent the electrode shaft portion from being bent by preventing the electrode from rising excessively.

The discharge lamp according to claim 1 is a pair of an arc tube, a sealing portion formed at both ends of the arc tube, and a pair of electrodes that are held by the sealing portion and are opposed to each other in the arc tube. A discharge lamp comprising: an electrode of the first electrode; and a coil portion attached to the electrode so as to extend along a central axis of the electrode.
The electrode includes an electrode shaft portion, and an electrode main body portion thicker than the electrode shaft portion integrally formed at the tip of the electrode shaft portion, and the coil portion is separated from the electrode shaft portion. It is arranged so as to surround the side surface of the electrode shaft portion in a state, and is fixed only to the electrode main body portion.

  A discharge lamp according to a second aspect is the discharge lamp according to the first aspect, wherein a tip portion of the coil portion is fixed to a flat surface formed on a rear side of the electrode main body portion.

  The discharge lamp according to claim 3 is the discharge lamp according to claim 1, wherein the coil portion is disposed so as to be separated from the electrode shaft portion and surround a side surface of the electrode shaft portion; It is comprised with the outer side coil part arrange | positioned so that the outer side of the said inner side coil part may be surrounded.

The discharge lamp of the present invention includes an electrode including an electrode shaft portion and an electrode main body portion thicker than the electrode shaft portion integrally formed at the tip of the electrode shaft portion, and the coil portion is the electrode. It arrange | positions so that the side surface of the said electrode axial part may be surrounded in the state spaced apart from the axial part, and is being fixed only to the said electrode main-body part.
Therefore, when the coil part is heated to a high temperature state when the discharge lamp is started, the heat of the coil part is transferred to the electrode body part thicker than the electrode shaft part, and the heat of the coil part is directly applied to the electrode shaft part. Therefore, the temperature rise of the electrode shaft portion can be suppressed. Therefore, it is possible to reliably prevent the electrode shaft portion from being bent.

FIG. 1 shows the overall configuration of the discharge lamp of the present invention. FIG. 2 is a cross-sectional view of an embodiment of an electrode in the discharge lamp of the present invention. 2A is a front view of the electrode, and FIG. 2B is a sectional view in the longitudinal direction of the electrode.
As shown in FIG. 1, the discharge lamp includes an arc tube 10, sealing portions 11 and 12, electrodes 13 and 14, coil portions 15 and 16, metal foils 17 and 18, and external leads 19 and 20. The discharge space 10A in the arc tube 10 is filled with 0.15 mg / mm ³ or more of mercury as a discharge medium, and a rare gas such as argon gas has a pressure of 13 kPa (pascal) in a steady state in order to improve startability. Further, for example, a halogen gas such as bromine for performing a halogen cycle in the discharge space 10A in the arc tube 10 is sealed so that it becomes 10 ⁻⁶ to 10 ⁻² μmol / mm ³ in a steady state. Has been. Note that a metal halide may be enclosed in the discharge space 10A as a discharge medium.

  The arc tube 10 is formed in a substantially spherical shape, and a spherical or elliptical discharge space 10A is formed therein. The arc tube 10 is made of, for example, quartz glass because it is necessary to transmit light emitted from the discharge space 10A and not to be thermally deformed even when the discharge lamp is turned on. . Bar-shaped sealing portions 11 and 12 are integrally and continuously formed at respective end portions of the arc tube 10. The sealing portions 11 and 12 are hermetically sealed by embedding metal foils 17 and 18 made of molybdenum, respectively. One end of each of the electrodes 13 and 14 is connected to the metal foils 17 and 18, and the other end is exposed to the discharge space 10 </ b> A in the arc tube 10. The electrodes 13 and 14 are arranged to face each other with a distance of 0.8 to 1.5 mm, for example.

  The electrode 13 includes a cylindrical electrode shaft portion 131 and an electrode main body portion 132 that is thicker than that and is integrally formed with the electrode shaft portion 131. The electrode shaft 131 has an outer diameter of 0.4 mm and a total length of 5 mm, and the electrode main body 132 has a maximum outer diameter of 2 mm and a total length of 1.5 mm. It is desirable that the outer diameter of the electrode shaft portion 131 is in a range of 20 to 70% with respect to the outer diameter of the maximum outer diameter portion of the electrode main body portion 132. As will be described in detail later, when the outer diameter of the electrode shaft portion 131 satisfies this range, heat transfer from the electrode main body portion 132 to the electrode shaft portion 131 is efficiently inhibited, and the temperature rise of the electrode shaft portion 131 is suppressed. be able to. The electrode 13 is formed into a desired shape by cutting a cylindrical tungsten material having a purity of 4N or higher. Thereby, the amount of impurities released into the discharge space 10A from the electrode shaft portion 131 and the electrode main body portion 132 protruding into the discharge space 10A can be reduced. Moreover, you may form by using the shaping | molding die comprised with a ceramic etc. Similarly, the electrode 14 includes a cylindrical electrode shaft portion 141 and an electrode main body portion 142 that is thicker than that and is integrally formed with the electrode shaft portion 141.

  As shown in FIG. 2, the electrode main body portion 132 includes a coil mounted portion 133 and reduced diameter portions 134, 135, and 136 in order from the root side. The coil mounting portion 133 is formed in a cylindrical shape having a flat surface 133A for fixing the coil portion, which extends in a direction orthogonal to the electrode shaft portion 131. On the distal end side of the coil mounting portion 133, truncated cone-shaped reduced diameter portions 134, 135, and 136 that are gradually reduced in diameter toward the electrode distal end side are formed. By configuring the electrode main body 132 in such a configuration, a sufficient volume of the electrode main body 132 is ensured, and light emitted from a discharge arc formed between the pair of electrodes 13 and 14 is supplied to the electrode main body 132. Therefore, the light emission efficiency of the discharge lamp is high. The reduced diameter portion 136 formed at the forefront of the electrode main body 132 holds a discharge arc formed between the opposing electrodes 13 and 14. Similarly, the electrode main body portion of the electrode 14 includes a cylindrical coil mounted portion and a reduced diameter portion in order from the root side.

For example, the coil portion 15 is formed by spirally winding a φ0.2 mm tungsten wire so that the total length of the coil is 1 mm, the outer diameter of the coil is 2 mm, the inner diameter of the coil is 1.6 mm, and the pitch between the windings is 0. It is formed to be 2 mm. In the example of FIG. 2, the outer diameter of the coil portion 15 is substantially the same as the outer diameter of the maximum outer diameter portion (coil mounted portion 133) of the electrode main body portion 132. Moreover, the coil part 15 is comprised with the tungsten wire whose purity is 4N or more. By configuring the coil unit 15 with a high-purity tungsten wire, the amount of impurities released from the coil unit 15 exposed to the discharge space 10A of the arc tube 10 is reduced. The coil portion 15 surrounds the side surface of the electrode shaft portion 131 and is disposed in a posture extending in parallel with the electrode shaft portion 131 at a predetermined distance from the electrode shaft portion 131, and the tip surface thereof is flat in the coil mounted portion 133. It is fixed to the surface 133A by spot welding, for example.
In addition, in the example of FIG. 2, the coil portion 15 is arranged so that the plane in contact with each winding portion of the coil portion 15 is the same plane as the cylindrical coil mounted portion 133. When the maximum outer diameter portion (coil mounting portion 133) of the electrode main body 132 is sandwiched between two virtual planes that are separated from each other and extend in parallel with the electrode shaft portion 131, the coil portion 15 is sandwiched between the two virtual planes. It may be arranged inside the region. If the coil part 15 is arranged in this way, there is an advantage that the total width of the electrode shaft part 131 and the coil part 15 can be reduced, which is particularly advantageous when the inner volume of the arc tube 10 is small. For example, when the electrode shaft portion 131 is φ0.5 mm and the tungsten wire constituting the coil portion 15 is φ0.2 mm, the total width of the electrode shaft portion 131 and the coil portion 15 is 0.9 mm.
The coil portion 15 is fixed to only the flat surface 133A of the coil mounted portion 133 and is in a so-called cantilever state, but does not come into contact with the electrode shaft portion 131 due to the rigidity of the coil portion 15. The distance between the coil portion 15 and the electrode shaft portion 131 is preferably in the range of 10 μm to 1 mm. The coil portion 16 is disposed at a predetermined distance from the electrode shaft portion 141 of the electrode 14 in the same manner as the coil portion 15 and is fixed to the electrode main body portion 142.

  Note that it is not necessary for all the winding portions 151 in the coil portion 15 to be separated from the electrode shaft portion 131, and a part of the winding portion 151 may be in contact with the electrode shaft portion 131. That is, the meaning that the coil portion 15 and the electrode shaft portion 131 are separated from each other means that all the winding portions 151 in the coil portion 15 are separated from the electrode shaft portion 131 as shown in FIG. The coil portion 15 includes at least a part of the winding portion 151 that is separated from the electrode shaft portion 131.

  One end of each of the external leads 19 and 20 is connected to the metal foils 17 and 18, and the other end protrudes from the sealing portions 11 and 12 to the outside. The external leads 19 and 20 are made of molybdenum in the same manner as the metal foils 17 and 18. By applying a predetermined voltage to the external leads 19 and 20, an arc discharge is generated between the electrodes 13 and 14 disposed opposite to each other in the discharge space 10A, and mercury as a discharge medium evaporates to generate a predetermined mercury vapor pressure. As a result, light having a wavelength unique to mercury is emitted. The voltage applied between the external leads 19 and 20 is, for example, an AC voltage of 50 to 150 V (volts), the lamp current is 1 to 7 A (amperes), and the mercury vapor pressure in the discharge space 10A during lighting is 150. Above atmospheric pressure.

The operation at the start of the discharge lamp will be described. The first stage of discharge is mercury arc discharge starting from mercury adhering to the electrodes 13 and 14. This mercury arc discharge lasts until mercury attached to the electrode is blown away from the electrode. However, in the mercury arc discharge, the electrode is not heated to a temperature sufficient for thermionic emission.
The second stage of discharge is glow discharge. During this glow discharge, the electrode is heated by the collision of rare gas and mercury cations, and in particular, the irregularities on the surface of the coil portion 15 attached to the electrode 13 are easily heated, so that the coil portion 15 is in a high temperature state. When the electrode body 132 is heated to a temperature at which heat can be emitted by receiving heat transfer from the coil section 15, arc discharge starting from the reduced diameter portion 136 formed in the electrode body 132. Migrate to

  In the discharge lamp of the present invention, even if the coil part 15 is heated during the glow discharge and the coil part 15 becomes high temperature, the heat of the coil part 15 is directly transmitted to the electrode main body part 132. There is no direct heating by heat transfer from the part 15. In other words, since the coil portion 15 and the electrode shaft portion 131 are separated from each other, the heat transfer path length from the coil portion 15 to the electrode shaft portion 131 becomes longer. In addition, since the electrode shaft portion 131 is thinner than the electrode body portion 132, a heat dam is formed at the boundary between the electrode body portion 132 and the electrode shaft portion 131. As described above, since heat transfer from the coil portion 15 to the electrode shaft portion 131 is suppressed, the temperature of the electrode shaft portion 131 does not become excessively high. Therefore, the discharge lamp of the present invention can reliably prevent the electrode shaft portion 131 from being bent.

  FIG. 3 is a cross-sectional view of another embodiment of the electrode in the discharge lamp of the present invention. The electrode 13 shown in FIG. 3 includes an electrode shaft portion 131 and an electrode main body portion 132. The electrode main body 132 includes a coil mounted portion 133 and reduced diameter portions 134, 135, and 136. The electrode of FIG. 3 has the same structure as the electrode of FIG. 2 except for the connection structure between the coil portion 15 and the electrode main body portion 132. The outer diameter of the coil portion 15 in FIG. 3 is larger than the outer diameter of the electrode main body portion 132. The electrode 13 shown in FIG. 3 is disposed so that the winding portion 15A at the tip of the coil portion 15 surrounds the radial side surface 133B of the cylindrical coil mounting portion 133, and the coil portion 15A is covered by, for example, spot welding. It is fixed to the side surface 133 </ b> B of the mounting portion 133.

  FIG. 4 is a cross-sectional view of another embodiment of the electrode in the discharge lamp of the present invention. The electrode 13 shown in FIG. 4 includes an electrode shaft portion 131 and an electrode main body portion 132. The electrode main body 132 includes a coil mounted portion 133 and reduced diameter portions 134, 135, and 136. The electrode of FIG. 4 has the same structure as the electrode of FIG. 2 except for the connection structure between the coil portion 15 and the electrode main body portion 132. The electrode of FIG. 4 is arranged so that the most advanced winding portion 15A of the coil portion 15 surrounds the radial side surface 133B of the cylindrical coil mounted portion 133, and for example, the side surface 133B by spot welding or the like. In addition, the winding portion 15B following the winding portion 15A is fixed to the flat surface 133A of the coil mounted portion 133 by spot welding in the same manner as the winding portion 15A.

  FIG. 5 is a cross-sectional view of another embodiment of the electrode in the discharge lamp of the present invention. FIG. 5A is a front view of the electrode, and FIG. 5B is a cross-sectional view in the longitudinal direction of the electrode. The electrode 53 in FIG. 5 includes an electrode shaft portion 531 and an electrode main body portion 532. The electrode shaft portion 531 includes, in order from the electrode main body portion 532 side, the first electrode shaft portion 531A, the reduced diameter portion 531B whose outer diameter gradually decreases as the distance from the electrode main body portion 532, and the first electrode shaft portion 531A. And a second electrode shaft portion 531C having a thin outer diameter. The electrode main body 532 includes a coil mounted portion 533 and reduced diameter portions 534, 535, and 536, similar to the one shown in FIG. The coil mounting portion 533 is formed in a columnar shape having a flat surface 533A for fixing the coil portion 15 extending in a direction orthogonal to the electrode shaft portion 531. The coil portion 15 is disposed in a posture that surrounds the side surface of the electrode shaft portion 531 and extends in parallel with the electrode shaft portion 531 at a predetermined distance from the electrode shaft portion 531, and the tip portion thereof is a flat surface of the coil mounting portion 533. For example, it is fixed to 533A by spot welding or the like. In the example of FIG. 5, the coil portion 15 has a flat surface in contact with each winding portion of the coil portion 15 that is the same plane as the cylindrical coil mounted portion 533. When the coil portion 15 sandwiches the maximum outer diameter portion (coil mounted portion 533) of the electrode main body portion 532 between two virtual planes that are separated from each other and extend in parallel with the electrode shaft portion 531 in the same manner as the electrode of FIG. , It is preferable that they are arranged inside a region sandwiched between the two virtual planes. Although illustration is omitted, in the electrode of FIG. 5, similarly to the electrode of FIG. 3, the coil portion 15 is disposed so as to surround the radial side surface of the coil mounting portion 533, and the side surface of the coil mounting portion 533 is arranged. The coil portion 15 may be fixed by spot welding or the like.

  In the electrode of FIG. 5, a heat dam is formed at each of a boundary portion between the electrode main body portion 532 and the first electrode shaft portion 531A and a boundary portion between the first electrode shaft portion 531A and the reduced diameter portion 531B. Therefore, in the electrode of the embodiment of FIG. 5, two heat dams are formed, and heat is hardly transferred from the coil portion 15 to the second electrode shaft portion 531C, so that the temperature of the second electrode shaft portion 531C further increases. Can be suppressed.

  FIG. 6 is a cross-sectional view of another embodiment of the electrode in the discharge lamp of the present invention. The electrode 63 in FIG. 6 includes an electrode shaft portion 631 and an electrode main body portion 632 that is thicker than the electrode shaft portion 631 and is integrally formed with the electrode shaft portion 631. The electrode main body 632 includes a coil mounted portion 633 and reduced diameter portions 634, 635, and 636 in order from the root side. The coil mounting portion 633 is formed in a cylindrical shape that spreads in a direction orthogonal to the electrode shaft portion 631. On the distal end side of the coil mounted portion 633, truncated cone-shaped reduced-diameter portions 634, 635, and 636 that are gradually reduced in diameter toward the distal end side of the electrode are formed.

  The coil portion 15 surrounds the side surface of the coil mounted portion 633, and is arranged in a posture extending in parallel with the electrode shaft portion 631 at a predetermined distance from most of the coil mounted portion 633, and the coil portion 15 is wound on the foremost side. Only the wire 15 </ b> A is fixed to the side surface of the distal end portion of the coil mounted portion 633 by, for example, spot welding. A plurality of winding portions on the tip side of the coil portion 15 may be welded to the side surface of the coil mounted portion 633. 6 has a heat dam formed at the boundary portion between the coil mounted portion 633 and the electrode shaft portion 631, and the heat transfer from the coil mounted portion 633 to the electrode shaft portion 631 is hindered. The temperature rise of 631 is suppressed.

FIG. 7 is a cross-sectional view of another embodiment of the electrode in the discharge lamp of the present invention. The electrode 73 shown in FIG. 7 includes an electrode shaft portion 131 and an electrode main body portion 132. The electrode main body 132 includes a coil mounted portion 133 and reduced diameter portions 134, 135, and 136. The coil mounting portion 133 is formed in a columnar shape having a flat surface 133A for fixing the coil portion 75. The electrode of FIG. 7 has the same structure as the electrode of FIG.
The coil portion 75 has a two-layer winding structure including an inner coil 751 and an outer coil 752 wound around the inner coil 751. The inner coil 751 surrounds the side surface of the electrode shaft portion 131 and is disposed in a posture extending parallel to the electrode shaft portion 131 at a predetermined distance from the electrode shaft portion 131, and the winding 751A on the distal end side is attached to the coil. It is fixed to the flat surface 133A of the part 133 by, for example, spot welding. The outer coil 752 is disposed so as to surround the inner coil 751, and the winding 752 </ b> A on the distal end side is welded to the flat surface 133 </ b> A in the same manner as the inner coil 751. However, only one of the inner coil 751 and the outer coil 752 may be fixed to the flat surface 133A. In forming the two-layer winding structure of the coil portion 75, either a single tungsten wire is overlapped and wound, or two independent tungsten wires are individually wound. You may do it. 7 is a two-layer winding, but may be a three-layer winding or more.

FIG. 8 is a cross-sectional view of another embodiment of the electrode in the discharge lamp of the present invention. The electrode 83 in FIG. 8 includes an electrode shaft portion 531 and an electrode main body portion 532. The electrode shaft portion 531 includes, in order from the electrode main body portion 532 side, a first electrode shaft portion 531A, a reduced diameter portion 531B whose outer diameter gradually decreases as it moves away from the electrode main body portion 532, and the first electrode shaft portion 531A. And a second electrode shaft portion 531C having a thin outer diameter. The electrode main body 532 includes a coil mounted portion 533 and reduced diameter portions 534, 535, and 536, similar to the one shown in FIG. The coil mounting portion 533 includes a flat surface 533A for fixing the coil portion 15 that extends in a direction orthogonal to the electrode shaft portion 531. The electrode 83 in FIG. 8 is the same as the electrode in FIG. 5 except for the structure of the coil portion 85.
The coil portion 85 has a two-layer winding structure including an inner coil 851 and an outer coil 852 wound around the inner coil 851. The inner coil 851 surrounds the side surface of the first electrode shaft portion 531A and is disposed in a posture extending in parallel with the first electrode shaft portion 531A at a predetermined distance from the first electrode shaft portion 531A. The wire 851A is fixed to the flat surface 533A of the coil mounted portion 533 by, for example, spot welding. The outer coil 852 is disposed so as to surround the inner coil 851, and the winding 852 </ b> A on the distal end side is welded to the flat surface 533 </ b> A in the same manner as the inner coil 851.

  As described above, in the discharge lamp of the present invention, even when the coil portion is heated during the initial start-up glow discharge and arc discharge, the coil portion is attached only to the electrode main body portion and separated from the electrode shaft portion. Therefore, since the heat of the coil portion is not directly transmitted to the electrode shaft portion, it is possible to suppress the temperature rise of the electrode shaft portion, and thus reliably prevent the electrode shaft portion from being bent. There is an effect that can be.

1 shows the overall configuration of a discharge lamp of the present invention. Sectional drawing of the Example of the electrode in the discharge lamp of this invention is shown. Sectional drawing of the other Example of the electrode in the discharge lamp of this invention is shown. Sectional drawing of the other Example of the electrode in the discharge lamp of this invention is shown. Sectional drawing of the other Example of the electrode in the discharge lamp of this invention is shown. Sectional drawing of the other Example of the electrode in the discharge lamp of this invention is shown. Sectional drawing of the other Example of the electrode in the discharge lamp of this invention is shown. Sectional drawing of the other Example of the electrode in the discharge lamp of this invention is shown. The whole structure of the conventional discharge lamp is shown. Sectional drawing of the Example of the electrode in the conventional discharge lamp is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Arc tube 11,12 Sealing part 13,14 Electrode 131 Electrode axial part 132 Electrode main part 133 Coil mounting part 134,135,136 Reduced diameter part 15,16 Coil part 17,18 Metal foil 19,20 External lead

Claims (3)

An arc tube, a sealing portion formed at both ends of the arc tube, a pair of electrodes that are held by the sealing portion and are spaced apart from each other in the arc tube, and a central axis of the electrode In a discharge lamp comprising a coil portion attached to the electrode so as to extend along
The electrode is composed of an electrode shaft portion, and an electrode main body portion thicker than the electrode shaft portion formed integrally with the tip of the electrode shaft portion,
The discharge lamp, wherein the coil portion is disposed so as to surround a side surface of the electrode shaft portion in a state of being separated from the electrode shaft portion, and is fixed only to the electrode main body portion.   The discharge lamp according to claim 1, wherein a distal end portion of the coil portion is fixed to a flat surface formed on a rear side of the electrode main body portion.   An inner coil portion disposed so as to surround the side surface of the electrode shaft portion apart from the electrode shaft portion; and an outer coil portion disposed so as to surround the outer side of the inner coil portion. The discharge lamp according to claim 1, comprising:

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