JPH0673854U - Metal vapor discharge lamp - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide a metal vapor discharge lamp that prevents blackening of the inner wall of the arc tube, maintains a good luminous flux maintenance rate, and has a long life. A neck portion having a diameter smaller than that of a central portion is formed at an end portion of a ceramic tube, the end portion of the neck portion is sealed by a cap of a conductive cermet, and the surface of the cap inside the arc tube. In a ceramic arc tube having a concave space formed by locating the position at the neck part, a metal pipe having halogen resistance between the coil provided at the electrode tip of the electrode mandrel embedded in the conductive cermet and the conductive cermet. Is attached.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a metal vapor discharge lamp.

[0002]

[Prior art]

 Compared with metal halide lamps for general lighting, the operating temperature of the lamps is raised, and in order to obtain higher efficiency and better color rendering properties, the arc tube made of quartz has a higher heat resistance than quartz and is chemically stable. Various attempts have been made to use a translucent alumina ceramic tube having excellent properties.

As an arc tube of a metal halide lamp using this type of ceramic arc tube, for example, an arc tube having a structure shown in FIG. 3 disclosed in Japanese Patent Laid-Open No. 52-71695 is proposed. In the figure, reference numeral 21 denotes a ceramic arc tube, and a conductive cermet end cap 22 made of alumina and tungsten metal is hermetically sealed at both ends of a straight pipe by a sealing agent 23. An electrode mandrel 25 having a tungsten coil 24 at its tip is embedded inside the tube of the cap, and a lead rod 26 is embedded on the outside. A rare gas is enclosed in the tube together with mercury and a metal halide.

Further, in order to realize a short arc type ceramic arc tube, to prevent heat loss from the end, and to effectively use the luminous flux from the arc tube in combination with a reflecting mirror. , An arc tube having a characteristic shape has been proposed. That is, as shown in FIG. 4, a neck portion 12 having a diameter smaller than that of the central portion is formed at the end portion of the ceramic tube 11, and the surface position of the end closing cap 13 inside the arc tube is located at the neck portion. The arc tube is formed by forming a concave space.

[0005]

In the arc tube of FIG. 3 in which the electrode and the sealing part to which the electrode is attached are arranged in a straight line, the coldest part exists on the sealing part side from the coil at the tip of the electrode. In the arc tube in which the metal halide is enclosed, the evaporation temperature of the metal halide is affected by the above-mentioned temperature of the coldest part, which in turn affects the emission spectrum of the lamp. When the vapor-liquid equilibrium vapor pressure of the enclosed metal halide is low, for example, dysprosium iodide, the intensity of its continuous emission spectrum increases as the temperature of the coldest part increases.

Further, in the discharge space of the arc tube, when the temperature of the coldest part is low, the excessively enclosed metal halide exists in the coldest part in the liquid phase, and the supply amount of vapor to the discharge space is reduced. . This is inconvenient for the following reasons. At the start of discharge, the electrode tip is sputtered by the rare gas and the electrode material adheres to the arc tube wall. The adhered electrode material returns to the electrode tip again due to the halogen dissociated by the heat of discharge of the metal halide and the convection of the gas in the arc tube. However, if the temperature of the coldest part is low, the amount of halide vapor supplied to the discharge space is low, so the efficiency with which the electrode material adhering to the tube wall returns to the electrode tip again decreases. In other words, every time the arc tube starts to discharge, the amount of electrode substance attached to the tube wall increases and the tube wall becomes black. Therefore, the transmissivity of the arc tube decreases and the luminous flux emitted from the arc tube decreases.

In the arc tube of FIG. 4, in which the ceramic tube has a neck portion having a diameter smaller than that of the central portion and the surface position inside the arc tube of the closing cap is located at the neck portion to form a concave space, this concave space is the maximum. It becomes a cold part. Furthermore, the tip of the electrode and the embedded portion have a predetermined distance in order to protect the portion of the closed cap where the electrode mandrel is embedded from the heat of the arc. That is, since the concave space is deep, the metal halide liquid phase easily accumulates here, and the evaporation amount is small. Therefore, the arc tube having the concave space has a drawback that the tube wall is likely to be blackened.

[0008]

[Means for Solving the Problems]

 In the arc tube shown in FIG. 4, the neck portion having a diameter smaller than that of the central portion is formed, and the surface position of the closing cap in the arc tube is positioned at the neck portion to form the concave space. In order to raise the temperature of this space, a halogen-resistant pipe of molybdenum metal, for example, is attached to the electrode mandrel in the concave space, and this molybdenum pipe is heated by the heat from the arc. By raising the temperature, evaporation of the metal halide is promoted, and the blackening of the inner wall of the arc tube due to the sputtering of the material at the tip of the electrode caused by blinking of the arc tube can be prevented. By preventing blackening, the luminous flux maintenance factor can be kept good and the life of the arc tube can be extended.

[0009]

【Example】

 An embodiment of the present invention will be described with reference to FIG. An end cap 32 made of conductive cermet and made of convex alumina tungsten is hermetically sealed to the end of the translucent alumina tube 31 via a sealing agent 33. Further, a tungsten coil 34 is wound around the tip of the end cap at the center of the inner end surface of the pipe, and a molybdenum pipe 39 is welded to the electrode mandrel 35 made of tungsten. 36 are embedded and fixed. The other end of the arc tube has a structure in which an alumina tube and a conductive cermet are integrally sintered without using a sealing agent.

An alumina layer 37 having a thickness of 1 mm or less is integrally sintered with the conductive cermet end cap, which is the base, on the surface of the end cap exposed to the inner surface of the arc tube, and the electrical insulation is ensured. It has a designed structure. This prevents discharge from the surface of the end cap, which makes the arc unstable and prevents flickering of light and uneven color. Further, 38 indicates a surplus additive of metal halide.

The molybdenum pipe attached to the electrode mandrel is located between the tungsten coil attached to the tip of the electrode and the inner surface of the cermet cap, but its outer diameter does not exceed the outer diameter of the tungsten coil. This is to prevent discharge from the molybdenum pipe.

As the arc tube constructed as described above, an arc tube having an inner diameter of 10 mm, an end portion (neck diameter) of 4 mm, an arc length of 5 mm and a total length of 35 mm is used as an arc tube having indium iodide, lithium iodide, and thallium iodide. A trial was made of a 150-w metal halide lamp with dysprosium iodide, a predetermined amount of mercury, and an argon gas of 50 torr as a starting rare gas. Fig. 2 shows the change over time in the luminous flux of the lamp over a period of about 1000 hours, with and without the molybdenum pipe attached to the electrode mandrel (marked with ▲). The luminous flux maintenance characteristics are better when a molybdenum pipe is attached.

[0013]

[Effect of device]

 As is clear from the above description, in the metal halide lamp according to the present invention, the surplus additive aggregates in the recess formed in the electrode neck at the end of the arc tube when the arc tube is lit, but the amount of iodide evaporated from this increases. Then, the halogen cycle in which the electrode tip material attached to the inner wall of the arc tube is returned to the electrode tip again can be activated to prevent a decrease in luminous flux due to blackening of the arc tube.

[Brief description of drawings]

FIG. 1 is a view showing an arc tube of the present invention.

FIG. 2 is a diagram showing the change over time in the luminous flux of the lamp of the present invention and the conventional lamp.

FIG. 3 is a diagram showing a conventional arc tube.

FIG. 4 is a diagram showing a conventional arc tube.

[Explanation of symbols]

 31 Alumina Tube 32 End Cap 33 Sealing Agent 34 Coil 35 Electrode Mandrel 39 Metal Pipe

Claims (1)

[Scope of utility model registration request] 1. A ceramic tube is formed with a neck portion having a diameter smaller than that of a central portion at the end portion, the end portion of the neck portion is sealed by a cap of a conductive cermet, and the inside of the arc tube of the cap is formed. In a ceramic arc tube in which the surface position of the is located in the neck part to form a concave space, there is halogen resistance between the coil provided at the electrode tip of the electrode mandrel embedded in the conductive cermet and the conductive cermet. A metal vapor discharge lamp, which is equipped with a metal pipe.