JPS62131465A - High-pressure discharge lamp - Google Patents

Abstract

PURPOSE:To keep the efficiency of a high-pressure discharge lamp high and reduce the irregularity of color of emitted light, by covering a vertically-lit light emission tube with a heat retainer made of a light-permeable material and having prescribed form and dimensions. CONSTITUTION:A heat retainer 11 is made of a light-permeable material such as quartz glass and shaped as a cylinder closed at the bottom thereof and covers a light emission tube 1 and has such dimensions that the open bottom of the heat retainer is located between the tip of a lower main electrode 2b and the bottom of the light emission tube. When the light emission tube 1 is lit in a vertical position in an outer tube 3 as an upper main electrode 2a is located on the upside, a gas sealed in the outer tube is convected because of the presence of the heat retainer 11 so that the temperature of the bottom of the light emission tube becomes lower than that of any other portion thereof. As a result, an unevaporated metal halide is gathered to the bottom of the light emission tube 1 to reduce the irregularity of color of emitted light. Since the bottom of the light-permeable heat retainer 11 acts to suppress the convection of the gas at the bottom of the light emission tube 1, the light emission is not damped.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention relates to a high pressure discharge MC lamp such as this BA'd metal halide lamp.

[Conventional technology]

Figure 7 is a front view of a conventional vertical lighting type metal halide lamp, in which the main electrode on the base side is above the other living electrode. has a pair of live electrodes 2a and 2b,
The inside of the tube is filled with rare gases, mercury, and metal halides from the lid, some of which remain without evaporating during lighting. Reference numeral 3 denotes an outer tube that houses the arc tube 1, and an inert gas such as nitrogen gas is sealed inside. a base attached to the upper end of the fourth person 3 and electrically connected to the main electrodes 2a and 2b;
Reference numeral 5 denotes a heat insulating film provided at the lower end of the arc tube 1, and is formed of, for example, a zirconia film. 6 is an auxiliary electrode to facilitate starting, 7 is an auxiliary electrode 6 during lighting.
8 is a resistor for current-limiting the discharge between the auxiliary electrode 6 and the main electrode 2a at the time of starting, that is, the auxiliary discharge.

The above-mentioned high-pressure discharge lamp is lit with the cap 4 facing upward, and in this lighting state, light is emitted by gas convection within the arc tube l and inert gas convection within the outer bulb 3. The lower end of the tube 1 is cooled and becomes the coldest part. The vapor pressure of the metal halide remaining without evaporation adheres to this coldest part, and the vapor pressure of the metal halide is determined depending on the temperature of the coldest part. The heat retaining film 5 is provided for the purpose of increasing the temperature at the coldest point in order to optimize this vapor pressure and increase efficiency.

The technology for providing this heat-retaining film 5 is, for example, the Japanese Patent Publication No. 43-247.
It is shown in the 02+5 publication. On the other hand, the method of increasing the coldest point temperature using the heat insulating film 5 has the following drawbacks.

a) The heat insulating film 5 absorbs a portion of the light, and even if the light is reflected, the arc may absorb the light when the source passes through the arc again, and the light output is substantially attenuated.

b)'''A:, A:, Thermal insulation film 5 because the output cannot be increased
can be attached to the sides of the arc, making it impossible to raise the temperature of the coldest part to the optimum value.

For the above-mentioned reasons, there is a method in which a translucent heat insulator is used instead of the heat insulating film 5, and the temperature of the coldest part is increased by suppressing convection without reflecting light.
This method is disclosed in Japanese Patent Application Laid-open No. 58-137953 and Japanese Unexamined Patent Publication No. 137954/1983.

FIG. 8 is a front view showing a metal halide lamp according to this method, which shows a cylindrical heat insulating body 10 made of quartz that does not use a heat insulating film and has a transparent part I except for the sunrise part of the main electrode 2b. This covers the main electrode 2a. This heat insulator 10
Since the bottom is closed, it has the effect of blocking convection.
= Since it is translucent, the light output is hardly attenuated. By using this heat insulating body 10, efficiency increases by about 30% compared to a method using a heat insulating film.

[Problem that the invention seeks to solve]

A conventional high pressure discharge lamp is constructed as described above, and has a heat insulator 10.
In lamps using this method, there was a problem in that the color temperature of each emitted color varied greatly. For this reason, especially when illuminating with two or more lamps, there is a problem in practical use that 1/C unevenness occurs in the emitted light color.

This invention was made to solve the above-mentioned problems, and has a lamp efficiency higher than that of a method using a heat-retaining film.
Moreover, it is an object of the present invention to obtain a high-pressure discharge lamp that can reduce the /6 variation in color @degree compared to any of the conventional systems.

[Means for solving problems]

In the high-pressure discharge lamp according to the present invention, a cylindrical light-transmitting heat insulating body with a closed top is attached to the arc tube, and the lower open end of the heat insulating body is positioned between the lower main electrode and the lower end of the arc tube. This is what I did.

[For production]

In the high-pressure discharge lamp according to the present invention, the light emitting percentage is set higher than the temperature at the lower end by placing the arc tube from above with a transparent heat insulator. Halides are collected in a narrow area at the lower end of the arc tube, and the vapor pressure of the metal halide is determined only by the temperature at this lower end. The variation in the emitted light color is smaller than when it was used. Lamp efficiency is improved because the lower end of the heat insulator suppresses convection at the lower end of the arc tube, and the heat insulator does not attenuate the force and light emitted by its translucency.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, numerals 1 to 9 are the same as those of the conventional lamp shown in FIG. Reference numeral 11 denotes a heat insulating body made of quartz glass, which is a translucent cylinder that extends over the entire y of the light emitting V+ from above. In order to pass the lead wire 12 and the lead wire 13 of the auxiliary electrode 6, as shown in FIG.
8- slits 14 are provided. The inner diameter of the heat insulating body 11 is 4 degrees and the wall thickness is 2III! , the length is 83.

The lower end of the heat insulator 11 is open, and this open tin is connected to the jb between the tip A of the lower main electrode 2b and the lower end B inside the arc tube 1.
J, in this example, is at a position 5.5 wm from A or B, which is the middle of the distance 11 sam from A to B. The inner diameter of the luminescent v1 is 19.5 + W, the outer diameter is 23 mm, and the distance between the electrodes is 42 m. Inside the luminescent tube, for example, 20 cm of sodium iodide, 7 mg of scandium iodide, and 5 mg of mercury are contained in the luminescent tube.
2 mq and 30 Torr of argon. On the other hand, nitrogen gas is inside the outer tube 3 at 360 Torr.
It is enclosed.

Next, a comparative example between a conventional lamp and a lamp according to the present invention will be described. In the conventional example (I) using the heat insulating film 5 shown in FIG. 7, the lamp efficiency is 100 tm/w.
, twice 2σ of the product moment deviation of color temperature due to differences in lamps is 3
00, and in the conventional example (II) using the heat insulator 10 shown in FIG. 8, the lamp efficiency is l 22 t
m/w and the color temperature 2σ was 630, whereas in this invention the lamp efficiency was 116 Am/w and the color temperature 2σ was 120.

As described above, it was found that although the lamp efficiency was slightly lower than that of the conventional example (11), the fluctuation in color temperature was extremely small.

Therefore, the inventors conducted a detailed study on the conventional example (old lamp light color variation or large problem), and found that the heat insulating lO
By increasing the temperature of the coldest part, that is, the temperature of the lower end, in order to improve the lamp efficiency, the temperature difference between the temperature of the parts other than the lower end of the arc tube 1 is reduced, and the unevaporated filler is It was found that it spread over a wide area on the inner wall of the arc tube. In other words, the vapor pressure of gold rice and rogides inside the arc tube is determined by the position and temperature at which they adhere, so if the area where they adhere expands, the difference in the adhesion position by just 71" and the temperature distribution on the wall of the arc tube will increase. It is assumed that the vapor pressure fluctuates depending on the difference in the vapor pressure.It is also assumed that as the vapor pressure inside the arc tube increases, convection increases, and that the temperature on the inner wall of the arc tube becomes more and more uniform due to this convection. It would be better to use a platform to raise the temperature of the base of the tube, and to raise the temperature of other parts of the arc tube more than that.We are considering a method of installing a translucent heat insulator from the top of the arc tube to prevent heat loss due to convection. did.

FIG. 4 shows an example of the experimental lamp. According to this, the results of measuring the color temperature and lamp efficiency by changing the length of heat insulating body 1 and changing the position of the lower end are shown in Figures 5 and 6.
As shown in the figure. As the distance t (FIG. 4) from the tip of the main electrode 2b to the end face of the heat insulating body in the lower part of FIG. 5 is changed from 2 cm to 0 cm, the variation in color temperature is reduced from negligible. The variation in color temperature is constant up to t-1,1crnf, that is, the lower end of the interior of the arc tube, and increases rapidly beyond that point. Therefore, it can be seen that the variation in color temperature is relatively small if the lower round part of the heat insulating body 11 reaches the lower end of the interior of the arc tube. Furthermore, until the lower end of the heat insulator 11 handles the entire inside of the arc tube, the inclusions are collected at the lower end, and as the lower end of the heat insulator 11 moves further downward, the inclusions widely cover the tube wall. 1. In other words, until the lower end of the heat insulating body 11 or the entire inside of the arc tube is covered, the difference in temperature between the lower end of the arc tube and the temperature of other parts is small, so that the enclosed material is at the lower end. As a result, it was confirmed that the variation in color temperature among lamps was reduced.

On the other hand, from Figure 6, the lamp efficiency is t from 2crn to 1crn.
It can be seen that it gradually rises to n, then rapidly rises from 1 crn to Ocm, and then remains constant at so. It can be seen that if the lower end of the heat insulator is located below the tip of the main electrode 2b, the lamp efficiency will be sufficiently higher than the conventional lamp efficiency. In this way, t changes from 1crn to 2cn1
The reason for the rapid increase in efficiency is that even though the heat insulator is not located at the lower end of the arc tube, it is located above, which suppresses convection and lowers the coldest point temperature. It is thought that this will increase rapidly. The reason why the lamp efficiency decreases when the lower end of the heat insulator 11 is below the lower end of the arc tube is thought to be that the filler spreads on the inner wall of the arc tube and absorbs a portion of the light emitted from the arc. As described above, it can be seen that when the lower part of the heat insulator 11 is located between the tip A of the main electrode 2b and the lower end of the arc tube, a lamp with low Lang efficiency and small variations in light color can be obtained.

In the above example, the distance t between the heat insulator and the arc tube is 8.5 m, and the nitrogen filling pressure P in the outer tube is 360 Torr at room temperature.
However, it was found that the same level of lamp effect can be obtained even when the pressure is increased up to 680 Torr, and that the lamp efficiency decreases above that point. This is because convection between the arc tube and the heat insulator increases as the pressure increases, and the Reynolds number that governs such convection is proportional to the product of gas pressure and size, so IP < 5780 (Torr-
++m) shows that it is effective.

In addition, the upper end of the heat insulating body 11 is closed or has a slit 14 of 2 widths and 28 long fins, and this slit 1
The convection inside the warmer changes depending on the size of 4, but the lamp efficiency does not change even if the width is increased to 4, or if the width is increased further, the lamp efficiency gradually decreases, and below this level. In the case of the slit, th x can be regarded as closed.

Further, although the heat insulator 11 is made of quartz glass, it may be made of heat-resistant borosilicate glass or the like.

Further, in the embodiment, a 400 W metal/ride lamp is used, but the present invention is not limited to this, and the gas filled in the outer tube may also be other than nitrogen gas.

〔Effect of the invention〕

As explained above, according to the present invention, the arc tube is covered with a cylindrical light-transmitting heat insulator with a closed top, and the lower end of the heat insulator is positioned between the tip of the piezo electrode and the lower end inside the arc tube. This has the effect of providing a high-pressure discharge lamp with sufficiently high lamp efficiency and less unevenness in emitted light color.

[Brief explanation of drawings]

FIG. 1 is a front view of a high-pressure discharge lamp according to an embodiment of the present invention, FIGS. 2 and 3 are a plan view and a partially broken pressure surface view of a heat insulator, and FIG. 4 is a front view showing an example of an experimental lamp. Figure 5 is a characteristic diagram showing the relationship between the distance from the tip of the piezo electrode to the bottom end of the heat insulator and color temperature, and Figure 6 is a characteristic diagram showing the relationship between the distance from the tip of the main electrode to the bottom end of the heat insulator 1 and lamp efficiency. The characteristic diagrams shown in FIGS. 7 and 8 are front views of conventional high-pressure discharge lamps. DESCRIPTION OF SYMBOLS 1... Arc tube, 2a, 2b... Main electrode, 3... Outer tube, 6... Auxiliary electrode, 11... Heat insulator, 14...
slit.

Claims (2)

[Claims] (1) Equipped with a pair of main electrodes at both ends of the tube, and a rare gas inside the tube.
It is equipped with an arc tube filled with mercury and a metal halide in an amount that remains without evaporating during lighting, and an outer bulb filled with an inert gas. In a high-pressure discharge lamp that is lit above the electrodes, the arc tube is covered from above by a heat insulating body made of a cylindrical translucent member with a closed top, and the open lower end of the heat insulating body is connected to the lower main body. A high-pressure discharge lamp characterized in that the electrode is located between the tip of the electrode and the lower end of the arc tube. (2) 20 mg of sodium iodide, 7 mg of scandium iodide, 52 mg of mercury, 30 Torr of argon in the arc tube
2. The high-pressure discharge lamp according to claim 1, wherein the outer bulb is filled with nitrogen gas at 360 Torr.