JPH0145178B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to metal vapor discharge lamps such as high pressure sodium lamps. The present invention will be explained below using a high pressure sodium lamp as an example. As shown in Fig. 1, the high-pressure sodium lamp includes an electric introduction body 3 made of heat-resistant metal and an electricity introduction body 3 made of heat-resistant metal.
The electrode 6 fixed to the electrode 6 is attached to the cap 2 made of alumina ceramic or the like with a glass frit 5, and this is sealed to both ends of the arc tube body 1 made of alumina ceramic or the like with a glass frit 4, respectively.
Generally, the inside is filled with sodium, mercury, and a rare gas such as xenon (Xe) of several tens of torr as a starting gas. In FIG. 1, the parts with a dash attached are the same parts as the same symbols without the dash. Further, in order to lower the starting voltage, a starting aid 12 is attached to the arc tube body 1 as shown in FIG. 2, which is also known. Here, FIG. 2 is a mounting diagram of a lamp with a starting auxiliary body, and metal frame lines serving as input terminals are connected to heat-resistant metal electricity introduction bodies 3 and 3' at both ends of the luminous tube body 1 made of alumina ceramic or the like. 7 and 8 are fixedly connected via metal conducting wires 13 and 14, and a starting aid 12 made of a heat-resistant metal conducting wire is wound around the outer periphery of the arc tube body 1, and both ends thereof are electrically connected with glass beads 9 and 10. It is kept insulated and electrically connected to one of the input terminals (input terminal 7 in Figure 2) by the bimetal 11 only at the time of starting, and the starting voltage is reduced by shortening the distance between different poles at the time of starting. It is lowered to make starting easier. Furthermore, in recent years, in order to improve color rendering properties, the arc tube body 1
It has been proposed that a heat-resistant metal belt 18 as shown in FIG. 2 is wrapped around the end of the arc tube body 1 to raise the temperature of the coldest part at the end of the arc tube body 1. The metal belt 18 as described above insulates the coldest end of the arc tube 1, increases the vapor pressure of sodium within the arc tube 1, increases the resonance absorption of sodium, and spreads the emission spectrum to the entire visible range. plays a role in improving color rendering. Such a heat retention effect appears in the lamp's electrical characteristics as a lamp voltage. FIG. 3 shows the relationship between the width of the metal belt 18 and the potential gradient E (V/cm), and the lamp power and sodium molar ratio are constant. The potential gradient is the lamp voltage divided by the arc length (distance between electrodes), and is useful as a factor when the arc lengths are different. It can be seen that when the metal belt 18 is not attached (width = 0), the potential gradient is 12 V/cm, but when the width is increased to 5 m/m, the potential gradient can be increased to about 18 V/cm. Figure 4 shows xenon (Xe) pressure 20 Torr, sodium molar ratio
Potential gradient E of high pressure sodium lamp when 0.74
(V/cm) and the average color rendering index Ra. When the potential gradient E increases, Ra also increases, and even when the tube diameter increases, Ra also increases. However, regarding the latter tube diameter, arc tube materials such as polycrystalline alumina tubes with large tube diameters are expensive and not very common.
Therefore, it is common to use pipes with a diameter of up to about 10φ. The color rendering property of high pressure sodium lamp is Ra=40~70
Preferably Ra=50 to 60. If Ra is less than 40, it will be unsuitable as a light source for indoor lighting, and Ra
This is because when the value becomes 70 or more, the efficiency drops significantly. Therefore, if we try to obtain Ra40 by setting the tube diameter to 8φ in Figure 4, the potential gradient E will be 21V/cm, but at this time, the temperature of the sealed part A adjacent to the coldest part can be seen from Figure 4. The temperature will be around 770℃. When trying to obtain the preferable color rendering property Ra=60, the temperature of the sealed part is 800℃.
That's all there is to it. FIG. 5 is a plot of the thickness of the diffusion layer of sodium in the sealing glass after placing the sealing glass together with sodium in a container and allowing it to stand for a certain period of time at each treatment temperature, using the treatment temperature as a variable. (Mitsubishi Electric Technical Report, Vol47, No.11, 1973,
(See page 1177) From Figure 5, it can be seen that at temperatures above 750°C, sodium diffuses into the sealing glass in the form of a reaction. The processing temperature of the sealing glass in Figure 5 can be considered to be equivalent to the temperature of the sealing part A in Figure 4, so the temperature of the sealing part in Figure 4 is required to be 750°C or less. . In other words, when the temperature of the sealing area exceeds 750°C, sodium reacts with the sealing glass, causing
This tends to cause the sealing glass to become brittle, thereby shortening the life of the lamp. Average color rendering index
Ra is related to the potential gradient E, the tube diameter, and the molar ratio of sodium, but it is related to the temperature of the sealed part A in Figure 4.
It is thought that Ra's relationship will not change significantly. In other words, from Figure 4, if you want to obtain Ra = 60 at a temperature below 750°C, you will have to use an expensive arc tube with a large diameter equal to 12φ. The inventors conducted various studies in order to obtain a metal vapor discharge lamp with a small inner diameter of the arc tube, the temperature of the sealed part below a predetermined value, that is, a long life, and good color rendering properties. We found that this objective could be achieved by increasing the pressure of the rare gas containing xerin. Figure 6 shows a potential gradient of 15V/cm.
This figure shows the change in Ra when the xenon (Xe) pressure is changed, assuming a tube inner diameter of 8.0φ and a sodium molar ratio of 0.67. Here, the potential gradient is obtained by changing the tube input, and there is no heat insulator at the end. From FIG. 6, it can be seen that when the xenon (Xe) pressure is increased, Ra also increases. This means that xenon (Xe) atoms have some effect on the probability of resonance absorption of sodium atoms or molecules in the arc or in the vapor layer surrounding the arc. This invention was made by focusing on the effect of xenon (Xe) pressure on Ra as described above. That is, the metal vapor discharge lamp of the present invention includes an arc tube made of at least an oxide crystal such as polycrystalline alumina and has an inner diameter of 5 m/m to 12 m/m in the outer bulb, and is provided with a starting aid on the outer periphery of the arc tube. At least one end of the arc tube has a metal heat insulator with a width of 15 mm or less for insulating the end, and the arc tube is further filled with at least sodium and a rare gas containing xenon at 100 Torr or more. It is something. In this invention, the heat insulator increases the potential gradient of the arc tube to improve color rendering and luminous efficiency, and uses a metal belt,
Its width a is 0<a≦15 m/m. a＞15m/
In case of M, the temperature of the envelope reaches 800℃ or more, which significantly shortens the life of the envelope. Moreover, the metal vapor discharge lamp of this invention
Since the Xe sealing pressure is increased to 100 Torr, the starting voltage increases, so a starting aid is used to prevent this increase. The dotted line in Figure 4 is the potential gradient E when 300 Torr of xenon (Xe) is sealed, using the tube flow as a parameter.
The measurement results of the relationship between and the average color rendering index Ra are shown.
From this figure, if the xenon (Xe) pressure is set to 300 Torr, Ra = 60 can be achieved at the critical value of the sealing part temperature of 750° C. while keeping the tube diameter of the arc tube 11 at 8φ. If the tube diameter is further increased, Ra will be higher than that of xenon (Xe) at the same sealing temperature.
The same is true when the pressure is low. xenon pressure
It can be seen from Figure 6 that a value of 100 Torr or more is sufficient.
In other words, the variation in Ra is about ±3, but compared to normal
With respect to Ra at a xenon pressure of 20 Torr, it is only when the xenon pressure is 100 Torr or higher that the effect of improving the color rendering properties can be obtained beyond this variation. Furthermore, considering this variation at 100 Torr, the effect can be reliably obtained with a xenon pressure of 200 Torr or more. Also, if the pressure is over 500 Torr, the starting voltage will rise too much. That is, a xenon pressure of 200 Torr to 500 Torr is preferred. [Example] The lamp has a structure as shown in Fig. 2, has a bimetallic starter inside the outer bulb, and has an inner diameter of arc tube 1 of 8.0φ, distance between electrodes of 7.9cm, and a sodium amalgam ratio of 0.81.
When we prototyped a lamp with a xenon (Xe) filling pressure of 350 Torr, we obtained the following characteristics.

【table】

[Table] As described above, the present invention is a high-pressure sodium lamp in which a metal belt 18 is attached to the end of the arc tube 1 and a starting aid is provided around the outer periphery of the arc tube 1. The gas pressure is increased to achieve high color rendering, and the lamp has advantages such as being able to be manufactured at low cost, but the rare gas sealed in the arc tube 1 is not limited to only xenon (Xe). A mixture of xenon (Xe) and some other noble gas may also be used to produce a similar effect. Further, although the tube diameter of the arc tube is 8.0φ in the explanation of the main text, the same effect can be obtained if the tube inner diameter is 5 m/m to 12 m/m. A tube with a small inner diameter would be particularly applicable to low-power, high-pressure sodium lamps. If the inner diameter of the tube exceeds 12φ, the arc tube becomes expensive, and as is clear from FIG. 4, if the inner diameter of the tube is small, sufficient color rendering properties cannot be obtained, so it is necessary to use a tube with an inner diameter of 5φ or more. Figure 7 shows the fourth
From the data in the figure, the potential gradient E when giving Ra = 40
The inner diameter of the tube was replotted to obtain a straight line, and the potential gradient to make Ra = 40 for less than 5φ was calculated.
It is necessary to set the voltage to 18V/cm or more, and it can be seen from the sealing part temperature in Figure 4 that it exceeds the limit value of 750°C.
Therefore, the inner diameter of the pipe needs to be 5φ to 12φ. Furthermore, although a high-pressure sodium lamp was used in the explanation of this invention, it goes without saying that it can also be applied to other metal vapor discharge lamps such as metal halide lamps as long as sodium is sealed and the arc tube is an oxide crystal such as polycrystalline alumina. stomach. The heat insulating body may be provided at one end of the arc tube. When the inclusion is a sodium-mercury amalgam, the amalgam molar ratio ρ of sodium is preferably 0.1≦ρ≦1.0. This is because when ρ<0.1, the proportion of sodium is low, so the lamp voltage change due to sodium loss becomes large, which causes the lamp to turn off. The potential gradient E is determined from the relationship between the pipe diameter and the pipe wall load. The tube wall load ω _L is ω _L = W _L /πDla (W/cm ² )...(1) W _L : Tube power D: Tube diameter la: Distance between electrodes, and ω _L is for polycrystalline alumina It is desirable to use it at 20W/cm2 or ^less . Therefore, the potential gradient E is E=V _L /la (V/cm)...(2) Since V _L is the lamp voltage, E≦20πDV _L /W _L ...(3). When D=0.8cmφ V _L =130V W _L =360, E≦18.15. Equation (3) is the upper limit of the potential gradient E.

[Brief explanation of drawings]

Figures 1 and 2 are front views showing the arc tube of a high-pressure sodium lamp and the configuration in which the arc tube is mounted; Figure 3 is a diagram showing the relationship between belt width and potential gradient;
Figure 4 is a diagram showing the relationship between potential gradient or sealing part temperature and average color rendering index Ra; Figure 5 is a diagram showing the relationship between sealing glass processing temperature and the thickness of the sodium diffusion layer; Figure 6 shows the effect of xenon (Xe) pressure on the average color rendering index Ra, and Figure 7 re-plots the potential gradient and pipe inner diameter when Ra = 40 is given from the data in Figure 4, and draws a straight line. This is the diagram obtained. In addition, the same reference numerals in the figures indicate the same or equivalent parts, 1 is the arc tube, 2 is the cap, 3 is the electric introduction body, 6 is the electrode, 7 and 8 are the metal frames, 11 is the bimetal, and 12 is the starter complement. , 18 is a metal belt.

Claims (1)

[Scope of Claims] 1. The outer bulb includes at least an arc tube made of an oxide crystal such as polycrystalline alumina and has an inner diameter of 5 m/m to 12 m/m, and a starting aid is provided on the outer periphery of the arc tube, and At least one end of the tube has a metal heat insulator with a width of 15 m/m or less for insulating the end, and the arc tube contains mercury as well as sodium, and the amalgam ratio of this sodium is 0.1 to 1.0. , and the pressure of the rare gas containing xenon is 200 to 500 Torr, and the average potential gradient E of the lamp when lit is E≦20πDV _L /W _L (V/cm), where D: tube inner diameter ( cm), V _L : lamp voltage W _L : metal vapor discharge lamp, characterized in that it is the lamp power.