JPS62200646A - High pressure sodium lamp with good color rendering property - Google Patents

Abstract

PURPOSE:To improve the lamp efficiency and secure a long service life, by exposing the outside of the tube end of an alumina tube without using a heat insulator film, and making the outside of the alumina tube into the coolest portion. CONSTITUTION:An exhaust pipe 3 with an electrode 2 penetrating the tube end 1a of an alumina tube 1 is prepared, for example. While the surrounding wall of the exhaust pipe 3a and the hole edge of the tube end 1a are enclosed by a sealant 5, sodium is, together with a shock absorber gas, sealed in the alumina tube 1 through the exhaust pipe 3a, and the outer end is sealed up. Since the alumina tube 1 is exposed not only at the middle portion but also at the tube end like this, as well as the efficiency is improved, the service life can be extended by making the outside of the alumina tube into the coolest portion.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention has a color rendering index (Ra) of 60 or more and a color temperature of 23.
The present invention relates to a so-called high color rendering type high pressure sodium lamp of 00''K or higher.

[Prior Art] Conventionally, high color rendering type high pressure sodium lamps have been known (
For example, Japanese Patent Application Laid-Open No. 57-55052), this high-pressure sodium lamp requires the temperature of the coldest part to be raised to a certain degree, so the end of the alumina tube, which is the arc tube, is covered with a heat-retaining film such as tantalum foil.

[Problems to be solved by the invention] In high-pressure sodium lamps with a small rated input (150W or less), the input is small in relation to the capacity of the end of the arc tube, so in order to obtain a specified temperature at the coldest part, It is necessary to increase the width of the heat insulating film (in the longitudinal direction of the arc tube), resulting in a problem that the efficiency of the lamp deteriorates. This tendency is particularly noticeable in high-pressure sodium lamps whose exhaust pipe material has the coldest part outside the arc tube, so the mainstream for low-power lamps has been to have the coldest part inside the arc tube.

Additionally, there is a known high-pressure sodium lamp that uses an irregularly shaped alumina tube in which the diameter of the end portion is smaller than the diameter of the middle portion, in an attempt to improve efficiency by reducing the heat capacity of the end portion of the arc tube. (Japanese Unexamined Patent Publication No. 57-53059), however, irregularly shaped alumina tubes require more sophisticated manufacturing techniques than straight alumina tubes, and are also more expensive.

On the other hand, in a high-pressure sodium lamp whose coldest part is inside the arc tube, amalgam (Na+8g) remains at the end of the arc tube during lighting. This is illustrated in FIG. 1. That is, a buffer metal and sodium are sealed in the alumina tube l.

In a high-pressure sodium lamp in which an electrode 2 is enclosed via a niobium tube 3, the amalgam 6 accumulates on the tube end la of the alumina pipework.In the figure, 4 is an end cap, and 5 is a sealant.

When the amalgam remains at the end of the arc tube in this way, a liquid reaction progresses between the sodium in the amalgam and the arc tube 1 (alumina) and the sealant 5, and as a result, the amount of sodium in the amalgam decreases, causing the amalgam to There was a problem in that the composition of the lamp changed and the light color of the lamp changed.

On the other hand, as shown in Fig. 2, there is an exhaust pipe material in which the coldest part is outside the alumina pipe, that is, an electrode is placed at the end of the alumina pipe l.
An exhaust pipe (niobium pipe) 3a having a
In a high-pressure sodium lamp in which sodium is sealed together with a buffer metal inside the alumina tube l via the alumina tube l and sealed, the coldest part is the end of the exhaust pipe 3a, that is, the outside of the alumina tube l.

Surplus amalgam 6 accumulates in the chain portion. This result 1 arc tube 1
, the sealant 5 and sodium cause a gas-solid reaction,
The reaction rate was slower than that of the liquid-intermediate reaction, and there was no significant decrease in sodium, which was desirable in terms of longevity.

This invention was made based on the above knowledge, and aims to improve the efficiency and life of the lamp at the same time.

[Means for solving problems] The high color rendering type high pressure sodium lamp of this invention is.

Buffer metal, sodium, and electrodes are sealed in a straight alumina tube, and the rated input is 150W or less.The outer end of the alumina tube is exposed without using a heat insulation film, and the coldest part is It is characterized by the exterior of the alumina tube.

In the above, it is desirable to make the thickness of the end of the alumina tube as thin as possible to reduce the heat capacity of the end.

[Function] According to the high color rendering type high pressure sodium lamp of the present invention, not only the middle part of the alumina tube but also the tube ends are exposed, so that efficiency can be improved and at the same time, the coldest part is outside the alumina tube. So the lifespan can be extended.

[Example] The present invention will be described in detail below. Figure 3(a) and (
b) shows the high-pressure sodium lamp of the example, and (a) shows the end 1a of the alumina tube l made thinner than usual (approximately 2.5 m).
m) L/1 An exhaust pipe (niobium @) 3a having an electrode 2 is provided through the pipe end la, and the circumference of the exhaust pipe 3a and the hole edge of the pipe end 1a are sealed with a sealant 5. , the exhaust pipe 3
Sodium is sealed together with a buffer gas into the alumina tube 1 via a, and the outer end of the exhaust pipe 3a is sealed. In addition, (b) is almost the same as (a), but the tube end 1a is made thinner (approximately 1.9 mm), and the end cap 4 is superimposed on the outside of the tube end 1a. and Endora cap 4 are also bonded via sealant 5. In this case, the total thickness of the tube end 1a and Endora cap 4 is:
The thickness was the same as in (a), but it was thinner than the normal one. Although one end of the alumina tube l is shown on each side, it is constructed in the same way as the other end. Moreover, it goes without saying that the high pressure sodium lamp has an alumina tube 1 constructed as above 1 and further held within the outer sphere, and high pressure sodium lamps as above 0 are manufactured with rated inputs of 50 W, 70 W and 150 W, Each sought efficiency. First, in the case of 50W, the inner diameter of the alumina tube l is 4 mm, and the wall load is 4 mm.
4 W/cm''.The efficiency as a lamp was 501/W at a color temperature of 2500°K.

For 70 v, the inner diameter of the alumina tube 1 was 5 mm, and the wall load was set to 37 W/cm''. The efficiency was 52 m/w at a color temperature of 2500 °k.

In the case of 150 W, the inner diameter of the alumina tube 1 was set to 6.6 mm, and the wall load was set to 34 W/c rn'.

The efficiency was 65 m/w at a color temperature of 2500 °K.

Table 181 shows the above results when compared with a conventional high-pressure sodium lamp, that is, an alumina tube in which a heat insulating film of tantalum or the like is provided on the outside of the tube end. 1.43 at 50W
1.37 times at 70W.

At 150W, the efficiency was improved by 1.25 times.

Next, we conducted a lighting test on the 50W high-pressure sodium lamp and obtained the results as shown in Figures 4 and 5. In Figures A is the example, and B is the conventional lamp. Both Muammalgam fleas are the same, but in the conventional one, the outside end of the alumina tube is insulated, and
The high-pressure sodium lamp of the example, in which the coldest part is inside the alumina tube (end), has a nearly constant lamp voltage for approximately 9,000 hours, and has little change in color temperature, extending its lifespan. I was able to confirm that it is possible.

[Effects of the Invention] As explained above, according to the present invention, there is an effect that it is possible to provide a high color rendering type high pressure sodium lamp which improves lamp efficiency and at the same time extends its life.

Table 1 (comparison of efficiency)

[Brief explanation of drawings]

1 and 2 are partial sectional views of a conventional high-pressure sodium lamp, FIGS. 3(a) and 3(b) are partial sectional views of an embodiment of the present invention, and FIG. 4 is a partial sectional view of the embodiment and a conventional product. FIG. 5 is a diagram showing the relationship between lighting time and lamp voltage, and FIG. 5 is a diagram showing the relationship between lighting time and color temperature. 1... Alumina tube 1a... Tube end 2... Electrode
3a... Exhaust pipe 4... End cap 5...
Adhesive Figure 3 (a) Figure 3 (b) Figure 5 Color temperature Tc ('K) Lighting time (hr)

Claims (2)

[Claims] (1) In a high-pressure sodium lamp in which buffer metal, sodium, and electrodes are sealed in a straight alumina tube and the rated input is 150 W or less, the outside of the alumina tube end is exposed without using a heat-retaining film, and A high color rendering type high pressure sodium lamp characterized by having the coldest part outside the alumina tube. (2) A high color rendering type high pressure sodium lamp according to claim (1), wherein the alumina tube has a thin end portion to reduce the heat capacity of that portion.