JP3136588U - Electrode assembly for high pressure discharge lamps - Google Patents

Abstract

An object of the present invention is to provide a simple means that does not require advanced techniques such as ultra-fine cutting on the rear end side of an electrode shaft of an electrode assembly used in a high-pressure discharge lamp at an axial position relative to the rear end side of the electrode shaft. Allow the metal foil to be welded.
An electrode shaft 3 of a tungsten electrode 2 and a metal foil 4 are connected to each other via a joint 6, and the joint 6 welds one end 6 a to the rear end portion of the electrode shaft 3, and the like. The end portion of the metal foil 4 welded to the end 6 b is formed of a crank-type refractory metal piece that holds the end of the electrode shaft 3 at the axis Y position.
[Selection] Figure 1

Description

The present invention relates to an electrode assembly used for a high-pressure discharge lamp used as a light source for a liquid crystal projector or the like.

A high-pressure discharge lamp used in a liquid crystal projector such as a data projector or a home theater projector, for example, as shown in FIG. A pair of electrode assemblies 20 and 20 welded so as to be serially connected to the wire 24 are inserted into both ends of a light emitting tube 25 made of a quartz glass tube and formed at an intermediate portion of the light emitting tube. 26, the electrodes 21 and 21 are arranged to face each other, and the rear end side of the electrode shaft 22, the metal foil 23, and a part of the power supply wire 24 heat-shrinks both end sides of the arc tube 25. It is embed | buried in the sealing parts 27 and 27 sealed airtight with the shrink seal | sticker.

Further, mercury, a halogen such as bromine, and a starting rare gas such as an argon gas are sealed in the light emitting portion 26 of the arc tube 25 and are evaporated from the tungsten electrode 21 while the lamp is turned on to emit the light emitting portion 26. The tungsten-halogen cycle action of re-evaporating tungsten adhering to the inner surface of the lamp and returning it to the electrode 21 prevents early blackening of the light emitting section 26 that impairs the lamp life, and the electrodes 21, 21 facing each other in the light emitting section 26. By reducing the distance between them and setting the arc length to 2 mm or less and the mercury encapsulation density in the light-emitting part 26 to 10 mg / ml or more, the mercury vapor pressure in the light-emitting part 26 is increased during lamp operation, thereby reducing the size and the point light source. High luminance emission close to is obtained. The electrode 21 is formed in a hemispherical shape or a spherical shape by heating and melting a tip portion of the electrode shaft 22 made of a tungsten rod and a part of the heat dissipation tungsten coil 28 wound around the tip side. (See Patent Document 1).
JP 2005-56646 A

FIG. 3 shows a processing procedure in which the tube end side of the arc tube 25 through which the electrode assembly 20 is inserted is heated and shrunk to form the sealing portion 27. First, the procedure is as shown in FIG. 20 is inserted into the tube of the arc tube 25 from the electrode 21 side, and then the arc tube 25 is heated and contracted first from the portion where the metal foil 23 of the electrode assembly 20 is inserted as shown in FIG. The contraction range is gradually expanded in both directions on the electrode shaft 22 side and the power supply wire 24 side of the electrode assembly 20 to seal the entire tube end side of the arc tube 25 as shown in FIG.

However, when the arc tube 25 is heated and shrunk first from the portion where the metal foil 23 of the electrode assembly 20 is inserted as shown in FIG. 3B, the metal foil 23 is moved along the tube axis of the arc tube 25 along with the contraction. In addition to the movement of the metal foil 23, the electrode shaft 22 of the electrode assembly 20 is tilted as shown in FIG. 3C with the joint P welded to the metal foil 23 as a fulcrum. When the electrode shaft 22 is inclined with respect to the tube axis X of the arc tube 25 and the tilt angle θ is large, an arc generated between the electrodes 21 and 21 contacts the inner wall of the light emitting portion 26 of the arc tube 25. As a result, devitrification of the light emitting portion 26, cracks due to thermal strain, and the like may occur, and the lamp life may be impaired. In addition, since the tilt angles and tilt directions of the electrodes 21 and 21 facing each other in the light emitting portion 26 of the arc tube 25 are different from each other, there is a problem that the light output of each lamp varies.

The tilting of the electrode shaft 22 as described above can be suppressed by welding the metal foil 23 to the rear end portion of the electrode shaft 22 at the position of the axis Y. For example, the known electrode shown in FIG. The rear end portion of the electrode shaft 32 is cut into a V shape, and a pair of inclined surfaces 34 and 34 are formed at the rear end portion with the axis Y of the electrode shaft 32 sandwiched therebetween, and one of the inclined surfaces 34 is formed. The metal foil 33 is welded to the rear end of the electrode shaft 32 at the position of the axis Y (see Patent Document 2).
Japanese Utility Model Publication No. 60-4361

However, in Patent Document 2, when the angle θ of each inclined surface 34, 34 formed by cutting the rear end portion of the electrode shaft 32 into a V shape as shown in FIG. If the thickness of the end portion is reduced and the mechanical strength is reduced, the end portion may be broken, and if the angle θ of the inclined surface 34 is larger than 45 degrees, an edge portion is formed and the electrode shaft 32 is moved behind. It has been pointed out that there is a risk of causing cracks in the sealed portion of the arc tube in which the end is embedded, and therefore the angle θ of each inclined surface 34, 34 is set within a range of 15 degrees to 45 degrees. However, the electrode shaft 32 in the same document is composed of a thin rod having a diameter of 2 mm, and the thin rod is further thinned from the front end side to the rear end side around which the heat radiation coil 38 is wound. As shown in Fig. 4 (a) Ku Narusuru that the predetermined angle of the inclined surface 34, 34 is cut in a V-shape is not easy, and requires a high degree of microfabrication technology. In particular, with the recent miniaturization of the lamp, the electrode shaft becomes thinner, and the electrode shaft used in the short arc type high-pressure mercury vapor discharge lamp with a rated lamp power of 150 W manufactured by the present applicant is: Since it is an extremely thin wire formed of a tungsten wire having a wire diameter of 0.3 mm, it is extremely difficult to perform ultra-fine processing by cutting the rear end portion into a V shape and cutting the slopes 34, 34 at a constant angle. The processing defect rate is inevitably high.

Further, as shown in FIG. 4B, the rear end portion of the electrode shaft 42 is cut into a half shape, and a metal foil 43 is welded to the half portion 44 so that the metal foil is placed on the axis Y of the electrode shaft 42. As shown in FIG. 4C, a slit groove 45 extending from the rear end along the axis Y is cut in the rear end portion of the electrode shaft 42, and the metal foil 43 is formed in the slit groove 45. An electrode is also known in which the end portion is inserted and the metal foil is welded to the position of the axis Y of the electrode shaft 42. However, the rear end portion of the electrode shaft 42 made of a thin tungsten rod is cut into a half shape or is slid Fine processing such as cutting the dividing groove 45 also requires advanced processing technology using a laser cutting device or the like (see Patent Document 3). In addition, the ultra-fine processing that cuts the half portion 44 and the slit groove 45 at the rear end of the electrode shaft formed of a tungsten wire having a wire diameter of 0.3 mm as described above requires extremely high precision processing technology. And
JP 2001-160374 A

For this reason, the conventional high-pressure discharge lamp is generally not processed as shown in FIGS. 4A to 4C at the rear end portion of the electrode shaft. Therefore, as shown in FIG. In many cases, the electrode 21 and its electrode shaft 22 are inclined with respect to the tube axis X of the arc tube 25.

Therefore, the present invention is advanced as shown in FIG. 4 in which the rear end portion of the electrode shaft is cut into a V shape to cut a slope, a half-cut shape, or a slit groove. It is a technical problem to enable metal foil to be welded to the rear end side of the electrode shaft at its axial position by a simple means that does not require a fine precision processing technique.

In order to solve the above problems, the present invention provides an electrode assembly for a high-pressure discharge lamp in which a metal foil and a power supply wire are welded in series to a rear end side of an electrode shaft of a tungsten electrode. The shaft and the metal foil are connected to each other through a joint. The joint is welded at one end to the rear end of the electrode shaft, and the end of the metal foil welded to the other end is the axis of the electrode shaft. It is formed of a crank-type refractory metal piece held in position.

According to the present invention, the electrode shaft and the metal foil are welded to each other through a joint formed of a crank-type refractory metal piece without subjecting the electrode shaft of the tungsten electrode to the high-precision processing as shown in FIG. With such a simple process, the metal foil can be welded to the rear end side of the electrode shaft at the axial position.

In the best mode of the electrode assembly according to the present invention, an electrode shaft of a tungsten electrode and a metal foil made of molybdenum foil are connected to each other through a joint, and the joint is connected at one end to the rear end of the electrode shaft. The end of the metal foil welded to the other end is formed of a crank-type molybdenum piece or tungsten piece that holds the axial position of the electrode shaft.

FIG. 1 is a view showing an example of an electrode assembly according to the present invention. For example, in an electrode assembly 1 used for a short arc type ultrahigh pressure mercury vapor discharge lamp having a rated lamp power of 150 W, an electrode shaft 3 of a tungsten electrode 2 has a wire diameter. A metal made of molybdenum foil having a thickness of 0.018 mm, a width of 1.5 mm, and a length of 15 mm, which is formed of a 0.3 mm tungsten wire and formed on the rear end side of the electrode shaft 3 at the left and right ends thereof at the knife edge. The foil 4 and a power supply wire 5 made of molybdenum wire having a diameter of 0.5 mm are welded so as to be connected in series. The electrode 2 is a hemispherical or spherical electrode having a diameter of about 1.0 mm by heating and melting the tip of the electrode shaft 3 and a part of the heat dissipation tungsten coil 7 wound around the tip. Is formed.

The electrode shaft 3 and the metal foil 4 are connected to each other via a joint 6 in which one end 6a is welded to the rear end portion of the electrode shaft 3 and the other end 6b is welded to the end portion of the metal foil 4. Crank-type refractory metal piece in which the joint 6 welds one end 6a to the rear end of the electrode shaft 3 and holds the end of the metal foil 4 welded to the other end 6b at the position of the axis Y of the electrode shaft 3 It is formed with. That is, when the joint 6 that connects the electrode shaft 3 and the metal foil 4 is welded at one end 6 a to the rear end of the electrode shaft 3, the end of the metal foil 4 welded to the other end 6 b is connected to the electrode shaft 3. It is formed of a refractory metal piece bent into a crank shape so as to be held at the axis Y position. Further, the crank-type refractory metal piece forming the joint 6 has a thickness of 0.035 mm corresponding to about twice that of the metal foil 4 and a width corresponding to one third of the metal foil 4. It is formed of molybdenum pieces or tungsten pieces having a length of 5 mm and a length of 2.0 mm.

As a result, the electrode assembly 1 is formed by simply processing the electrode shaft 3 and the metal foil 4 through the joint 6 formed of a crank-type refractory metal piece, and the metal foil 4 is attached to the electrode shaft 4. It is possible to weld the rear end side at the axis Y position.

Moreover, when the electrode assembly 1 in which the metal foil 4 is welded to the rear end side of the electrode shaft 4 at the axis Y position is embedded in the sealing portion of the arc tube, the electrode shaft 3 is connected to the metal foil 4. Therefore, the angle at which the electrode shaft 3 is inclined with respect to the tube axis of the arc tube can be kept small. Therefore, the lamp using the electrode assembly 1 has little variation in light output, and is less likely to cause devitrification and cracking of the light emitting portion due to the inclination of the electrode 2 and the electrode shaft 3.

The crank-type refractory metal piece forming the joint 6 has a thickness of 0.035 mm, which corresponds to about twice that of the metal foil 4 in order to impart rigidity sufficient to maintain its regularity. Selected. Further, the width is selected to be 0.5 mm corresponding to one third of the metal foil 4 so as not to apply much stress in the sealed portion of the arc tube.

The present invention contributes to improving the quality performance of a high-pressure discharge lamp used as a light source for a liquid crystal projector or the like.

The figure which shows an example of the electrode assembly which concerns on this invention A diagram showing a conventional electrode assembly and a high-pressure discharge lamp using the assembly. The figure which shows the procedure which produces the high pressure discharge lamp using the conventional electrode assembly, and the problem Figure showing a conventional electrode assembly

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electrode assembly 2 ... Tungsten electrode 3 ... Electrode axis
4 ... Metal foil
5 ... Power supply wire
6 ... Fitting

Claims (1)

In an electrode assembly for a high-pressure discharge lamp, in which a metal foil and a power supply wire are welded in series to a rear end side of an electrode shaft of a tungsten electrode, the electrode shaft and the metal foil are connected via a joint. The joint is a crank type refractory metal piece that is connected to each other and that welds one end to the rear end of the electrode shaft and holds the end of the metal foil welded to the other end at the axial position of the electrode shaft. An electrode assembly formed.

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