JPS62131460A - High-pressure metal vapor discharge lamp - Google Patents

Abstract

PURPOSE:To improve color rendition without increasing the load of the wall of a light emission tube and using a high-melting-point metal plate, by making the outside diameter of each end cap portion of the tube larger than that of the central portion thereof. CONSTITUTION:The outside diameter a of each end cap portion 1a of a light emission tube 1 is made larger than that (b) of the central portion thereof. The tube 1 is covered with a cylinder 8 of diffusion glass along the total length of the tube. Infrared rays emitted from the tube 1 are effectively reflected by the cylinder 8 to heighten the temperature of the tube, especially the temperature of the end cap portions 1a which are the lowest temperature of all the portions of the tube. As a result, the pressure of sodium vapor is increased to improve color rendition without heightening the load of the wall of the tube 1 and using a high-melting-point metal plate which would adversely affect the life of the tube.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-pressure metal vapor discharge lamp such as a high-pressure sodium lamp, and more particularly to a high-pressure metal vapor discharge lamp with improved color rendering properties.

[Background of the Invention] It is generally known that when the metal vapor pressure, for example, sodium vapor pressure, of a high-pressure metal vapor discharge lamp is increased to 00 Torr or more, the emission spectrum spreads over the entire visible range and color rendering properties are improved. However, there is a limit to increasing the tube wall load in order to increase the sodium vapor pressure. This causes the sodium sealed in the arc tube to react with the alumina material of the arc tube, causing sodium to disappear.

This is because the life of the discharge lamp will be shortened. Therefore,
Conventionally, a method has been used to increase the temperature of the arc tube by reflecting infrared rays of the synchrotron radiation, which have zero visibility, into the arc tube, thereby increasing the sodium vapor pressure. One method is to wrap a high melting point metal plate such as tantalum around the end of the arc tube, which is the coldest part of the arc tube, to raise the temperature. However, since this method brings the metal into direct contact with the high-temperature arc tube, there is a problem in that cracks occur at the interface due to heat shock, and it also requires the use of expensive high-melting point metals. be.

For this reason, for example, as described in Japanese Patent Application Laid-Open No. 59-187951, a method is adopted in which a diffuser tube for reflecting infrared rays is covered with an arc tube. The effect obtained by inverting this diffusion tube is good enough that the arc tube and diffusion tube are in close contact with each other. However, the temperature at the center of the arc tube is 110°C.
Since the temperature reaches 0℃, if the diffusion tube is tightly attached to the arc tube,
There is a problem in that a low-quality glass material cannot be used as the diffusion tube, and an expensive alumina pipe must be used.

[Object of the invention] The object of the present invention is to reduce the load on the wall of the arc tube without increasing the load on the wall of the arc tube.
Without using high-melting point metal plates that have a negative impact on lifespan,
An object of the present invention is to provide an inexpensive high-pressure metal vapor discharge lamp with excellent color rendering properties.

[Structure of the Invention] In order to achieve the above object, in the high-pressure metal vapor discharge lamp of the present invention, an arc tube made of translucent ceramic whose outer diameter at both end caps is larger than the outer diameter at the center is covered with a cylinder made of diffusion glass. .

[Function] With the above configuration, the cylinder made of diffusion glass and the arc tube are
Contact occurs only at the caps at both ends at around 800°C, and 11
A gap is formed between the outer periphery of the central part of the arc tube, which is exposed to a high temperature of 00° C., and the diffusion glass cylinder, so that they do not come into direct contact with each other.Therefore, the diffusion glass cylinder is not required to have as much heat resistance as alumina.

[Embodiments of the invention] An embodiment of the present invention will be described below with reference to the drawings.

In Figure 0, which is a cutaway diagram of the main parts of a high-pressure sodium lamp, electrode support tubes 2 and 3 are protruded from both ends of an arc tube 1 made of translucent ceramic, respectively.
are welded to conductor columns 6, 7 via conductors 4.5, respectively, and the arc tube 1 is supported within the lamp outer bulb (not shown).

The outer diameter a of the end cap portions 1a at both ends of the arc tube 1 (7) is larger than the outer diameter of the central portion 1b of the arc tube 1. The entire length of the arc tube 1 is covered with a cylinder 8 made of diffusion glass. As the diffusion glass, opaque quartz glass is used, which has a higher infrared reflectance than transparent quartz glass. Incidentally, the arc tube 1 may be one in which the end cap portion is integrally molded with the arc tube, or one in which the end cap portion is constructed separately from the arc tube body and joined with an adhesive or the like.

With such a configuration, the infrared rays emitted from the arc tube 1 are effectively reflected by the cylinder 8, and the temperature of the arc tube 1, especially near the end cap portion 1a, which is the coldest part, increases, and the sodium vapor pressure increases. As a result, color rendering properties are improved. At this time, since the portion of the arc tube 1 in contact with the cylinder 8 is the end cap portion 1a whose temperature reaches 800° C. at most, there is no problem even if the material of the cylinder 8 is quartz glass.

[Effects of the Invention] According to the present invention, the central part of the arc tube is made small in diameter, and the contact part with the cylinder is made into an end cap part where the temperature does not rise so high, so that the cylinder is made of diffusion glass whose heat resistance is not as high as that of alumina. It is possible to inexpensively increase the total vapor pressure and improve the color rendering properties.

[Brief explanation of drawings]

The figure is a sectional view of the main parts of a high-pressure sodium lamp according to an embodiment of the present invention. ■... Arc tube, 1a... End cap part, 1b... Center part, 8... Cylindrical made of diffusion glass.

Claims (1)

[Scope of Claims] A high-pressure metal vapor discharge lamp characterized in that an arc tube made of translucent ceramic whose outer diameters at both end caps are larger than the outer diameter at the center is covered with a cylinder made of diffusion glass.