JPH0656756B2 - Double-ended metal vapor discharge lamp - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a double-ended metal vapor discharge lamp.

2. Description of the Related Art In recent years, the use of high-pressure metal vapor discharge lamps represented by metal halide lamps and high-pressure sodium lamps as a light source for indoor lighting has been increasing. In particular, in the field of store lighting, in order to enhance the lighting effect on the displayed products, it is desired to develop a compact lamp that can easily control the light distribution and can downsize the fixture.

The double-ended metal vapor discharge lamp responds to such a demand, and has a structure shown in FIG. 2 when a metal halide lamp is taken as an example. In the figure, reference numeral 1 denotes an arc tube made of quartz, and a pair of electrodes 2a and 2b are hermetically sealed at both ends, and mercury, a rare gas and a predetermined metal halide are sealed inside. Reference numeral 3 is an outer tube made of high-silica-containing glass, for example, quartz, having crushing sealing portions 4a and 4b at both ends, and the inside is evacuated to a vacuum. Electrodes 2a and 2b are molybdenum foil 5a and
5b, current supply conductors 6a, 6b, molybdenum foils 7a, 7b of the outer tube sealing portion, and external lead wires 8a, 8b are electrically connected to the caps 9a, 9b. Reference numeral 10 is a getter for adsorbing and removing the impure gas in the outer tube 3, and 11 and 12 are heat insulating films applied to the outer wall surface of the arc tube near the electrodes.

In such a lamp, since the outer bulb is compact and it is difficult to incorporate a start-up assisting circuit in the outer bulb, the lamp is normally lit by using a built-in starter type ballast (not shown). That is, when the power is turned on, the secondary voltage of the ballast and the high-voltage pulse generated by the starter superposed on the secondary voltage of the ballast are applied between the electrodes 2a and 2b, and discharge is started between the electrodes 2a and 2b to start the lamp. .

Problems to be Solved by the Invention As described above, the outer tube of the double-ended metal vapor discharge lamp is evacuated to a vacuum, but during the life of the lamp, impure gas is released from the constituent members of the lamp, The degree of vacuum inside the outer tube gradually decreases. If the lamp does not start under these conditions, for example, a rise in the starting voltage causes a fault, a rise in the lamp voltage causes extinction, and a momentary drop in the power supply voltage causes the lamp to turn off. In such a case, the high voltage pulse from the ballast is applied between the current supply conductors 6a and 6b, so that the current supply conductor 6a
A discharge between a and 6b, that is, a discharge in the outer tube is easily generated. When such discharge in the outer tube occurs, the current supply conductor 6a,
6b may be melted and the outer tube 3 may be damaged.

The similar discharge in the outer tube is also caused by the leakage of the enclosed gas from the arc tube 1. In this case, the enclosed gas is an easily dischargeable gas, which is more dangerous.

The present invention has been made to solve the above problems, and provides a double-ended metal vapor discharge lamp that prevents discharge in the outer bulb and is not damaged during its life.

Means for Solving the Problems The present invention provides an arc tube in which at least mercury and a rare gas are sealed in a translucent heat-resistant container having a pair of electrodes, and a crushed seal portion is provided at both ends of the arc tube. And an outer tube for accommodating the above, and at least one of a pair of current supply conductors arranged between the crushed seal portion and the arc tube is provided with an insulating coating.

Action The above configuration can prevent discharge in the outer tube,
Due to this, it is possible to prevent the current supply conductor from being melted and the outer tube from being damaged.

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

FIG. 1 shows an embodiment of a double-ended metal halide lamp according to the present invention, which has a lamp power of 150 W.
Therefore, the light source is lit at a power supply voltage of 200 V using a ballast with a built-in starter. In FIG. 1, 13 is an arc tube made of quartz, and a pair of electrodes 14a and 14b are hermetically sealed with molybdenum foils 15a and 15b. Mercury, thulium iodide, dysprosium iodide, holmium iodide, sodium iodide, and thallium iodide are enclosed in the arc tube 13, and the radioactive isotopes krypton 85 of argon and krypton 85 are used as starting rare gases. It is sealed at a predetermined pressure. The distance between the electrodes is 17.5 mm, the inner diameter of the arc tube is 12.5 mm, and the heat insulating film 16 containing zirconium oxide as a main component is applied to the outer wall of the arc tube near the electrodes.

Reference numeral 17 denotes an outer tube made of quartz, and has crushed sealing parts 1 at both ends.
8a and 18b, and molybdenum foils 19a and 19b are used for the crushed sealing portion to supply current supply conductors 20a and 2b.
0b is hermetically sealed. The inner diameter of the outer tube is 20 mm, and the inside is evacuated to vacuum.

The electrodes 14a and 14b are molybdenum foils 15a and 15b, current supply conductors 20a and 20b, molybdenum foils 19a and 19, respectively.
b, the base 22a via the external lead wires 21a, 21b,
22b is electrically connected. An insulating tube 23 made of quartz covers one of the current supply conductors 20a.

Reference numeral 24 is a getter whose main component is a zirconium-aluminum alloy.

Here, since the current supply conductor 20a is covered with the insulating tube 23, it is possible to prevent discharge between the current supply conductors 20a and 20b, that is, discharge inside the outer tube, and to prevent damage to the outer tube during its life. Has become.

Hereinafter, specific examples of the present invention will be described.

In the lamp having the above structure, the insulating tube 23 has a wall thickness of 0.
Using a 5 mm quartz tube, assuming the vacuum degree inside the outer tube is reduced, the gas pressure inside the outer tube is 1 × 10 ^{-4 to} 50 Torr.
Prototype many lamps changed within the range of
After lighting for more than a certain time, the power was turned off momentarily to turn off the lamp, and then the power was turned on again, and it was observed whether discharge in the outer tube occurred before the lamp was restarted.

For comparison, the same experiment was conducted on the lamp having the conventional structure shown in FIG. In these experiments, argon was used as the fill gas in the outer tube.

The table below shows the results of these experiments.

As can be seen from the above table, in the conventional lamp, glow gas is generated in the outer tube until the gas is restarted when the gas pressure in the outer tube is within the range of 0.01 to 5 Torr, and the charged pressure is 5 Tor.
It can be seen that when rr is exceeded, arc discharge occurs in the outer tube. Both of the discharges in the outer tube are the current supply conductors 6a, 6
When the arc discharge occurs, the current supply conductor may be blown out by repeating the experiment.

On the other hand, in the lamp of the embodiment of the present invention, regardless of the gas pressure filled in the outer tube, no discharge occurs in the outer tube,
Of course, none of the current supply conductors melted down.

Although quartz is used as the insulating tube in the above embodiment, heat resistant glass other than quartz may be used, and the same effect can be obtained by using heat resistant ceramics such as alumina and zirconia. The present invention can also be implemented for high pressure sodium lamps and high pressure mercury lamps.

Further, although an insulating tube is used as the insulating coating in the above-mentioned embodiment, a heat resistant insulating paste containing alumina, silica, zirconia, magnesia, etc. as a main component is applied to the current supply conductor to form the insulating coating. It may be one.

EFFECTS OF THE INVENTION As described above, according to the present invention, at least one of the pair of current supply conductors disposed between the outer tube crushing seal portion and the arc tube is provided with an insulating coating, so that the discharge in the outer tube is prevented. (EN) It is possible to provide a double-ended metal vapor discharge lamp which is prevented and is not damaged during its life.

[Brief description of drawings]

FIG. 1 is a front view of a double-ended metal vapor discharge lamp which is an embodiment of the present invention, and FIG. 2 is a front view of a conventional double-ended metal vapor discharge lamp. 13 ... Arc tube, 17 ... Outer tube, 20a, 20b ... Current supply conductor, 23 ... Insulation tube.

Claims (1)

[Claims] 1. An arc tube having at least mercury and a rare gas sealed in a translucent container having a pair of electrodes, and an outer tube having a crushing seal portion at both ends and accommodating the arc tube. ,
A double-ended metal vapor discharge lamp in which at least one of a pair of current supply conductors arranged between the crushed seal portion and the arc tube is provided with an insulating coating.