JPS61135045A - High pressure sodium lamp for dc lighting - Google Patents

Abstract

PURPOSE:To avoid cataphoresis by locating the coldest area of a high pressure sodium lamp for DC lighting in the anode-side end of the emitter tube by installing a thermal protective film around the cathode-side end of the emitter tube. CONSTITUTION:A high pressure sodium lamp 21 for DC lighting is assembled by installing an anode 4, a cathode 5 and an alumina emitter tube 1 charged with a mixture of neon gas and argon gas in an outer tube 9 and installing a thermal protective film 12 prepared by winding a metallic foil made of tantalum around the cathode-side end of the emitter tube 1. The anode 4 is prepared by winding a tungsten coil around a bar made of thorium and tungsten. The cathode 5 is prepared in the same manner as the anode 4 and has a coil prepared by sintering and fixing an electron-emitting substance. Due to the above structure, the coldest area of the lamp 21 is located in the anode-side end of the emitter tube 1. Consequently, it is possible to avoid cataphoresis occuring during DC lighting, thereby preventing any luminance nonuniformity.

Description

[Detailed description of the invention] Industrial applications The present invention relates to high pressure sodium lamps.

The crystallization of conventional technology is progressing actively. In particular, in order to use high-pressure sodium lamps and metal halide lamps as the main light source for indoor lighting, we have developed SOW lamps with efficiency and high color rendering comparable to the luminous flux level of incandescent bulbs in the SOW ~160W class.
Attempts are being made to develop and commercialize compact 70W class high-pressure sodium lamps and metal halide lamps.

For example, the applicant proposed a new compact high-pressure sodium lamp with high color rendering properties in Japanese Patent Application Laid-open No. 57-9045 and Japanese Patent Application Laid-open No. 57-50763. The prototype high-pressure sodium lamp with high color rendering properties produced based on this proposal has a warm light color similar to that of a light bulb, and has a rung input of e.
Although it has a low wattage of sow, it is nearly three times more efficient than a light bulb. The arc tube of this lamp is thin, 6 to 7 mm thick, and very short, around 60 cm long, so a relatively small glass bulb with a shape similar to the arc tube of a halogen lamp is used to cover the lamp outer tube. The features of this arc tube should be fully demonstrated if it is used as a reflective device that is small in size and has a large degree of freedom in light distribution control, and is used by being attached to a lighting device. At the same time, there is a desire for lighting devices (circuits) to be smaller, lighter, and more efficient, and various electronic circuit ballasts are being tried to replace the conventional magnetic induction ballasts. n has arrived. Among these, a DC step-down chopper circuit type ballast has high circuit efficiency even though it is used for DC lighting, and is relatively inexpensive.

Furthermore, it is lightweight and can be downsized to the same size as the lamp itself. Therefore, it is considered that the present invention is most suitable as a lighting device for a compact, low-wattage high-pressure sodium lamp such as the one described above.

Problems to be Solved by the Invention However, a phenomenon common to discharge lamps is that when lighting with direct current, the light emission on the anode side becomes weak due to the cataphoresis phenomenon of the discharge body. This case was no exception; when the lights were turned on using a DC step-down chopper circuit, the light emission from the sodium atoms on the anode side became weaker, especially when the cathode side was facing downwards.

The present invention has been made to solve these problems, and an object of the present invention is to provide a high-pressure sodium lamp for direct current lighting that is free from uneven luminance.

Means for Solving the Problem In order to solve this problem, the high-pressure sodium lamp for direct current lighting of the present invention includes an arc tube with an anode and a cathode aligned, and the cathode side end of the arc tube is wound. This is a high-pressure sodium lamp for direct current lighting that is equipped with a thermal protection film.

Effect: With this configuration, the coldest point of the arc tube is shaded by the anode side tube end mK, so the cataphoresis phenomenon that accompanies DC lighting can be avoided.Therefore, there is no unevenness in luminous brightness and almost constant lighting characteristics. can get.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the structure of a 50 W high color rendering high pressure sodium lamp for direct current lighting, which is an embodiment of the present invention. In the figure, 1 is an alumina arc tube with an inner diameter of 6H at the center, that is, a maximum inner diameter, and the diameter is narrowed at both ends, and the outer diameter is 2
Electrode conductors 2 and 3 made of M niobium tubes are sealed. At the tips of the electrode conductors 2 and 3, n anodes 4. A cathode 6 is held. The anode 4 has a tungsten coil wound around an anode rod made of thorium or tungsten. On the other hand, the cathode 5 is thorium.

Place the tip of the tungsten cathode rod around the tungsten cathode rod.
A tungsten coil is wound with the wings protruding. In the space formed by the cathode rod and the tungsten coil, a triple coil made of tungsten in which an electron emitting material is sintered and fixed is inserted, and above it is a triple coil made of tungsten that does not contain any electron emitting material. is installed. Inside the arc tube 1, a mixed gas of neon and argon is sealed at about 60 Torr, with a partial pressure ratio of sodium amalgam 6 and starting aid gas to argon gas of about 60 percent. The arc tube 1 is connected to and held by lead wires 7 and 8 via electrode conductors 2 and 3, respectively, and has an inner diameter of 12.5 mm.
It is loaded into a straight glass outer tube 9 with an outer diameter of 15 mm and an outer diameter of 15 mm. The other end of the lead wire A, 8 is welded and connected to the end of the metal foil 10° 11 made of molybdenum,
The metal foils 10 and 11 are hermetically sealed at the ends of the outer tube 9. At the cathode side end of the arc tube '1, a metal foil made of mental material with a thickness of 20 μm is wound twice and attached to form a thermal protection film 1.
form 2. A ring-shaped getter holding material 13 is provided at the end of the arc tube 1 on the anode 4 side so as to surround the tube end, and this getter holding material 13 is held by the lead wire 7 via a getter support 14. ing.

The inside of the getter holding material 13 is filled with barium getter in advance, and after the outer tube 9 is evacuated to form the chip 12, the getter holding material 13 is heated from the outside using, for example, a high frequency heating device. flushed. As a result, a getter coating 15 made of barium is formed on the inner surface of the outer tube 9 closer to the chip 12.

A lighting test was conducted on the high-pressure sodium lamp 21 for direct current lighting with such a configuration using a direct current step-down chopper circuit (FIG. 2), which is one of the electronic circuit ballasts for direct current lighting. 201 is a 6oHz AC power supply, 202 is a bridge type full-wave rectifier circuit, and 203 is a smoothing capacitor. The smoothed DC voltage from both ends of the smoothing capacitor 203 is supplied to the DC step-down chopper circuit section on the right side of the figure. A high-pressure sodium lamp 21, a choke coil 204, and a power transistor 205 are connected in series, and a diode 20 is connected in parallel to the high-pressure sodium lamp 21 and choke coil 204.
6 is connected. The base and emitter of the power transistor 205 are connected to the control circuit 205,
The power transistor 20 is controlled by the action of the control circuit 207.
6) The high-frequency switching operation is repeated to operate the high-pressure sodium lamp 21. That is,
When the power transistor 206 is on, current flows from the high-pressure sodium lamp 21 to the choke coil 204 and to the power transistor 205, while when the power transistor 205 is off, current flows through the choke coil 204 and the diode 206 to the high-pressure sodium lamp 21. flows. Note that 208 in the figure is a starting circuit, which generates a high frequency pulse voltage when starting the lamp 21.

A high-pressure sodium lamp 2 for DC lighting as described above with a DC step-down chopper one-type electronic circuit ballast having such a configuration.
A lighting experiment was conducted. Constant lamp power 60W
So, I tried turning on the lamp by changing the position of the lamp. When the central axis of the high-pressure sodium lamp 21 is horizontal, the lamp voltage Vl during stable lighting and the color temperature Tc of the lamp emission color are shown in the table below when the cathode 6 is placed upward and the cathode 5 is placed downward.

As shown in the above table, it was found that the high-pressure sodium rung 21 was hardly affected by the lighting posture, and no uneven luminance occurred. This is because a thermal protection film 12 made of metal foil is formed on the cathode side end of the arc tube 1.
During lamp operation, this thermal protection film 12 functions to keep the cathode side end of the arc tube 1 warm, and even if the cathode 6 is lit with the downward position, the coldest point of the arc tube 1 is on the anode side. This is because it is formed at the end of the tube. As a result, the cataphoresis phenomenon accompanying DC discharge does not occur inside the arc tube 1, and a substantially constant discharge state can be achieved no matter what lighting position the lamp is in.

In the above embodiment, the case where the arc tube 1 is provided in a direction in which the cathode 5 is closer to the sealing part of the outer tube 9, that is, the base 16 has been described; It goes without saying that the same effect cannot be obtained even if the arc tube 1 is installed in the same direction.

On the other hand, when a thermal protection film is provided at both ends of the arc tube, or no heat protection film is provided at either end, as in the case of AC lighting, the coldest point of the arc tube 1 is always the cathode. Since it is formed at the side end, the discharge state is affected by the lighting orientation. That is, due to the cataphoresis phenomenon, the light emission of the IJ atoms on the anode side is weakened, resulting in uneven brightness in the arc tube. This brightness unevenness becomes most noticeable when the lamp is lit with the cathode side facing downward.

Although this embodiment shows an example of a straight tube lamp with a single cap as shown in FIG. 1, the same effect can be obtained in the case of a straight tube high pressure sodium lamp 22 with a double cap as shown in FIG. Needless to say, it will happen.

Furthermore, as in the present invention, the effect of suppressing the cataphoresis phenomenon of discharge by attaching a thermal protection film to the cathode end of the arc tube is common to high-pressure sodium lamps for direct current lighting, regardless of the configuration of the arc tube. However, as in this example, electrodes are placed on the inner surface of both ends of a small integrally formed alumina tube.
It has also been confirmed that the effect is most pronounced in high-pressure sodium lamps for direct current lighting in which electrode conductors are directly sealed.

Furthermore, in the case of a high-pressure thorium lamp for direct current lighting that has a protruding cathode rod and a cathode containing an electron-emitting substance inside, as in this example, a heat protector is provided at the end of the tube. The membrane also improves the stability of the cant spot during lamp operation, so that
Excellent movement characteristics with little variation in lamp voltage and light color can be obtained.

As described in detail, the high-pressure sodium lamp for direct current lighting of the present invention includes an arc tube having an anode and a cathode, and by providing a thermal protection film around the cathode side end of the arc tube, The coldest point of the arc tube during operation is formed at the anode side tube end. Therefore, the cataphoresis phenomenon that accompanies DC lighting can be avoided, and there is no unevenness in light emission brightness, and substantially constant lighting characteristics can be obtained. Furthermore, when the cathode has a bar-shaped configuration, excellent movement characteristics with less variation in lamp voltage and light color can be obtained.

[Brief explanation of drawings]

Figure 1 shows a high-pressure nut 1 for direct current lighting, which is an embodiment of the present invention.
, a partially cutaway front view of a 1-IJ lamp, FIG. 2 is a diagram showing an example of a lighting experimental circuit for a high-pressure IJ lamp according to the present invention, and FIG. FIG. 3 is a partially cutaway front view of the lamp. 1... Alumina arc tube, 2, 3... Electrode conductor, 4... Anode, 6... Cathode, 6
・・Mark・Sodium amalgam, 7, 8・・・Lead wire, 9・Old・・Outer tube, IQ. 11... Metal foil, 12... Heat protection film,
13...Getter holding material, 14...Getter support, 16...Getter coating, 16117
...Base, 21.22...High pressure sodium lamp, 201...AC power supply, 202...
...Full wave rectifier circuit, 203...Smoothing capacitor, 204...Choke coil, 206...
...Power transistor, 206...Diode, 2o7...Control circuit, 208...
starting circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure , -Afro, 7ya*,, Kanyo 2 Prisoner M3 figure

Claims (1)

[Claims] 1. A high-pressure sodium lamp for direct current lighting, comprising an arc tube having an anode and a cathode, and a thermal protection film wrapped around the cathode side end of the arc tube.