JPH0388257A - Single-sealing type metal vapor discharge lamp - Google Patents

Abstract

PURPOSE:To surely prevent discharge between electrode axis parts for preventing clouding of a bulb and deformation of electrode coil parts by covering the root parts of electrodes with quartz tubes while covering the tip parts of these electrode axis parts with ceramic tubes. CONSTITUTION:While electric axis parts 4, 4 are covered, on the sealing base edge parts sealed at a crushed sealing part 2, with quartz tubes 8, 8 the tip part sides near the electrode coil parts 5, 5 are covered with the ceramic tubes 9, 9 consisting of, for instance, high purity alumina linked with the quartz tubes 8, 8. Since in this way the tip parts of the electrode axis parts 4, 4 are covered with the ceramic tubes 9, 9 surpassing quartz in heat resistance, the ceramic tubes 9, 9 are free from erosion so that discharge between the electrode axis parts can be surely prevented while preventing clouding of a bulb 1 and deformation of the electrode coil parts 5.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION (Industrial Field of Application) The present invention relates to a single-sealed metal vapor discharge lamp that is applied to small metal halide lamps and the like. (Prior art) High-intensity discharge lamps, that is, high-pressure metal vapor discharge lamps (HID), which were traditionally used for outdoor lighting and factory lighting, are now often used for indoor lighting with low ceilings such as stores. It has become. The reason why lamps came to be used in stores, etc. is that arc tubes were made smaller, and along with this, the outer tube of the lamp was changed from hard glass to quartz, which is more heat resistant, and the outer shape was also made smaller and more compact. In addition to this, they can take advantage of the conventional characteristics of high efficiency, high color rendering, high output, and long life, so they can be used in place of incandescent or halogen light bulbs, making it possible to save energy. Can be mentioned. In particular, metal halide lamps are superior to other discharge lamps in terms of high efficiency and high color rendering, and are extremely suitable for illuminating displayed products, so they are becoming increasingly popular. By the way, when miniaturizing an arc tube, using a conventional valve structure with both ends sealed not only takes time and effort to mold, but also requires a large sealing section, resulting in a large shape. There are disadvantages such as increased heat loss from the arc tube through the arc tube. For this reason, in this type of small lamp, the arc tube has a so-called single-seal structure in which a crushed seal is formed at only one end of the bulb, and a pair of electrodes are sealed to this crushed seal end. We are hiring. In this way, since there is only one sealing part, the heat loss is smaller than that of a bulb with both ends sealed, which makes it possible to improve the luminous efficiency, and also eliminates the need for molding.
Moreover, since there is only one sealing part which has a relatively large shape compared to the size of the discharge space, there is an advantage that the whole can be made smaller. By the way, in such a single-sealed arc tube, a pair of metal foil conductors are sealed in the crushed sealing part, the shafts of the electrodes are connected to each of these metal foil conductors, and these electrode shafts are connected to the discharge space. electrode coil portions are provided at the tips of these electrode shaft portions so as to face each other. In electrodes with this structure, the distance between the opposing electrode shafts is smaller than in lamps with both ends sealed, so when the lamp starts, the arc spot that should normally be generated in the coil at the tip of the electrode moves and Arcs may occur at the base of the shaft, and arcs may occur between opposing electrode shafts. When such a discharge occurs, there are problems such as the electrode shaft being eroded and broken early, and the crushed sealing portion near the location where the discharge occurs being heated and causing cracks in the bulb. In order to solve this problem, it has been considered to cover the electrode shafts with a quartz tube to electrically insulate the electrode shafts and prevent discharge. (Three problems to be solved by the invention) However, even if the electrode shaft is covered with a quartz tube, the temperature at the tip of the electrode shaft becomes higher than the temperature at the proximal end, so the tip of the quartz tube melts due to heating. and may be eroded. If this condition occurs, the initial purpose of covering the quartz tube in preventing discharge cannot be sufficiently achieved, and the fused and scattered quartz may adhere to the wall of the bulb of the arc tube, causing the bulb to become cloudy or causing damage to the electrode coil. There are drawbacks such as adhesion and deformation of the electrode coil portion. The present invention was made based on the above circumstances, and provides a single-sealed metal vapor discharge lamp that can reliably prevent discharge between the electrode shaft parts, prevent clouding of the bulb, and deformation of the electrode coil part. This is what we are trying to provide. [Structure of the Invention] (Means for Solving the Problems) The present invention is characterized in that a quartz tube is placed over the base of the electrode shaft, and a ceramic tube is placed over the tip of the electrode shaft. (Function) According to the present invention, since the tip of the electrode shaft is covered with a ceramic tube that has better heat resistance than quartz, the ceramic tube will not be corroded even at high temperatures. It is possible to reliably prevent electric discharge between the electrode shaft portions, and prevent clouding of the bulb and deformation of the electrode coil portion. (Example) The present invention will be described below based on a first example shown in FIG. The drawing shows an arc tube of a 150 W metal halide lamp, and in the drawing, l is an arc tube bulb made of quartz glass, which is formed into a substantially ellipsoidal shape with an internal volume of 0.5 cc. In such an elliptical spherical valve l, the long sleeve direction is the valve axis, and a flat crushing sealing part 2 is formed at one end in a direction perpendicular to the valve axis. Inside the bulb 1, a pair of electrodes 3, 3 are arranged so as to be spaced apart from each other in the axial direction of the bulb, and these electrodes 3.3 are both sealed to the crush sealing part 2 on one side. The electrode 3.3 is composed of an electrode shaft part 4 and an electrode coil part 5. The electrode shaft part 4 is made of pure rhenium wire with a wire diameter of 0.5 mm, and the electrode coil part 5 is made of thoriated tungsten wire with a wire diameter of 0.5 au. It is formed of a wire and is wound three to four times around the bent tip of the electrode shaft section 4. These electrode coil portions 5.5 are opposed to each other at a distance of about 6III11 points (electrode open circuit M) along the valve axis direction. The electrode shaft portions 4.4 have a distance larger than the distance between the tips of the electrode coil portions 5.5, and are respectively connected to metal foil conductors 6.6 such as Mo or the like sealed to the crush sealing portion 2. It is connected. The metal foil conductors 6.6 are each connected to an external lead 7.7. The electrode shaft portion 4.4 is provided with a quartz tube 8°8 at the sealed proximal end portion sealed to the crushing seal portion 2, and at the tip close to the electrode coil portion 5.5. A ceramic tube 9.9 made of, for example, high-purity alumina is placed on the side of the quartz tube 8, and is connected to the quartz tubes 8, 8. The base end of the quartz tube 8.8 is embedded in the crushing sealing part 2 along with the electrode shaft 4.4, and the tip of the ceramic tube 9.9 is embedded in the crushing sealing part 2. The tip should protrude slightly. In addition, inside the valve l, there is a starting rare gas, a predetermined amount of mercury, 5n12, Na1s T(l I, Inl, NaB
Metal halides such as r, LiBr, etc. are enclosed. Further, in such a single-sealed metal halide lamp, the lamp current I during stable lighting is set to 1.8A, and the lamp input power W at this time is set to 150W. The inner surface area S of the arc tube is approximately 3.5 c-, and the lamp load per unit surface area of the arc tube is approximately 43 W/c.
-. The operation of the embodiment with such a configuration will be explained. In the electrode shaft portion 4.4, the sealed proximal end portion sealed to the crushing seal portion 2 is covered with a quartz tube 8.8, and the distal end portion near the electrode coil portion 5.5 is covered with a high-purity quartz tube. Since the electrode shaft portions 4.4 are covered with a ceramic tube 9.9 made of alumina, the electrode shaft portions 4.4 are insulated, thereby preventing discharge from occurring between the electrode shaft portions 4.4. Moreover, the tip side of the electrode shaft portion 4゜4, where the temperature increases during discharge, is covered with a ceramic tube 9 which has better heat resistance than quartz.
．． Since the ceramic tube 9.9 is covered with a ceramic tube 9.9, the ceramic tube 9.9 is not melted, and the insulation protection of the electrode shaft portion 4.4 is reliably maintained, and no melted material is scattered. For this reason,
The bulb is prevented from becoming cloudy, and there is no adhesion to the electrode coil portion 5.5, and deformation of the electrode coil portion 5.5 is also prevented. This results in a longer lamp life. It is possible to cover the sealed base end portions of the electrode shaft portions 4, 4 with a ceramic tube, but if this is done, the crushing may occur due to the difference in thermal expansion with the crushing sealing portion 2 made of quartz glass. This is not preferable because it causes cracks in the sealing part 2 or the ceramic tube. Further, the present invention is not limited to the above embodiments. That is, FIG. 2 shows a second embodiment of the present invention, in which a pair of electrode shaft portions 4.4 are inclined so that their distal ends widen from each other. That is, in this type of lamp, the coldest part may occur in the bulb wall A at the back of the electrode coil part 5.5, and the distance between this coldest part A and the electrodes 3, 3 should be made too small. In this case, the temperature of the coldest part A can be increased, and luminous efficiency and color rendering properties can be improved. For this reason, the electrode shaft portion 4,
In some cases, a configuration may be adopted in which the tip sides of the tubes 5 and 5 are spread apart from each other, and the electrode coil portion 5.5 is brought closer to the bulb wall A to raise the temperature of the coldest portion A. When configured in this way, the distance between the proximal ends of the electrode shaft parts 4, 4 sealed to the crushing sealing part 2 becomes relatively close to the distance between the electrode tips, and therefore, discharge is caused by the electrodes. Coil part 5.
5, but the probability of occurrence at I2 between the proximal ends of the electrode shaft portions 4.4, which is a relatively short distance, increases. Therefore, in the case of this embodiment, a quartz tube 8.8 and a ceramic tube 9 are attached to these electrode shaft portions 4°4, respectively.
．． Cover it with 9. Even with this configuration, electric discharge between the electrode shaft parts 4, 4 is prevented, and the electrode shaft part 4.4 is broken, the crush sealing part 2 is overheated, and cracks occur in the bulb. This prevents malfunctions and extends the service life. It should be noted that the present invention is not limited to metal halide lamps, but may be any discharge lamp in which a crushed seal is formed only at one end of the bulb. There may be. Further, the electrode may have a structure in which the electrode shaft portion and the electrode coil portion are integrally formed. [Effects of the Invention] As explained above, according to the present invention, the proximal end of the electrode shaft portion is covered with a quartz tube, and the distal end thereof is covered with a ceramic tube. prevent electrical discharge from occurring in the area. Therefore, breakage of the electrode shaft portion is prevented, and overheating of the crushing sealing portion is also prevented, thereby eliminating the occurrence of cracks in the bulb. In addition, the tip of the electrode shaft, where the temperature rises during discharge, is covered with a ceramic tube that has better heat resistance than quartz, so this ceramic tube will not melt, ensuring insulation of the electrode shaft. At the same time, the molten material is not scattered, the bulb is prevented from becoming cloudy, and there is no adhesion to the electrode coil portion, and deformation of the electrode coil portion is also prevented. This results in a longer lamp life.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a small metal halide lamp showing a first embodiment of the invention, and FIG. 2 is a sectional view of a small metal halide lamp showing a second embodiment of the invention. l... Arc tube bulb, 2... Crushing sealing part, 3...
Electrode, 4... Electrode shaft part, 5... Electrode coil part, 6...
... Metal foil conductor, 7... External lead wire, 8... Quartz tube, 9... Ceramic tube.

Claims (1)

[Scope of Claims] A crushed sealing portion is formed at one end of an arc tube made of quartz glass, and a pair of metal foil conductors is sealed to this crushing sealing portion, and the shaft portion of the electrode is attached to each of these metal foil conductors. connect and
In single-sealed metal vapor discharge lamps in which the electrode coil parts provided at the tips of the electrode shaft parts are opposed to each other in the discharge space, a quartz tube is placed over the base of the electrode shaft parts, and a quartz tube is placed over the base of the electrode shaft parts. A single-sealed metal vapor discharge lamp whose tip is covered with a ceramic tube.