JPH0519256B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a technology for preventing bursting of arc tubes in high-pressure sodium lamps. [Technical background of the invention and its problems] In general, high-pressure metal vapor discharge lamps do not have the function of limiting current by themselves, so they are used in combination with a ballast as a current limiter. Stabilizers are often made of chiyoke coils, which are made by winding insulated metal wire in multiple layers around an iron core, and other devices that also use capacitors. By the way, the lifespan of a ballast is usually 8 to 10 years, and the main cause of the lifespan is a decline in current limiting function due to deterioration of the insulator. In particular, high-pressure sodium lamps have a high starting voltage, so they are started by applying a high-pressure pulse for starting from a ballast or a pulse generator housed inside the lamp's outer bulb. Compared to ballast lamps and metal halide lamps, ballast insulation tends to deteriorate more quickly, and high-voltage pulses can force dielectric breakdown of ballasts that have begun to deteriorate. If the ballast loses its current limiting function at the end of its life or for other reasons, a large amount of current will flow through the lamp. This results in a sudden increase in the lamp input applied to the arc tube, causing the pressure of the inclusions inside the arc tube to rapidly build up, causing the arc tube to rupture, and even rupturing the outer bulb, causing the lamp itself or debris to fall. I'm worried. In order to prevent such dangers, the
96186 Publication" has been developed. In other words, this device uses a conductive wire with a fuse function as a part of the lead wire from the stem of the outer tube to the eyelet terminal of the base, and when an overcurrent flows, the conductive wire with the fuse function is instantly activated. This prevents the arc tube from bursting. However, when selecting a conductive wire with such a fuse function, it is not possible to make a judgment based solely on its ability to blow over current. It is necessary to consider the relationship with pressure. That is, when an overcurrent is applied to the arc tube, the temperature within the arc tube rises rapidly, and the gas pressure within the tube rises accordingly. As the gas pressure increases, the wall of the arc tube becomes unable to withstand it, resulting in cracks and rupture. The degree to which the gas pressure rises depends on the relationship between the magnitude of the input lamp current and the sealed gas pressure. However, since the charging pressure of the noble gas for starting a high-pressure sodium lamp is a factor that determines the lamp efficiency, the charging pressure may vary depending on the lamp rated value, or even if the rated value is the same. The fuse function cannot be selected simply by the fusing ability based on the overcurrent value. [Object of the Invention] The present invention has been made based on the above-mentioned circumstances, and an object of the present invention is to provide a light-emitting device to at least a portion of the internal lead wire introduced from the stem of the outer tube into the outer tube and connected to the arc tube. A high-pressure sodium lamp that uses a conductive wire with a fuse function that has a predetermined relationship with the starting rare gas sealed inside the tube, and can prevent the arc tube from bursting if excessive current flows through the lamp. This is what we are trying to provide. [Summary of the Invention] In other words, the present invention provides a high-pressure discharge lamp in which mercury, sodium, and a starting rare gas are sealed in an arc tube made of translucent ceramic, and this arc tube is housed in an outer tube with a cap attached to one end. In the sodium lamp, at least a part of the internal lead wire introduced from the stem of the outer bulb into the outer bulb and connected to the arc tube is composed of a conductive wire with a melting point of 800°C or more and 2000°C or less, and The cross-sectional area of the line is S
(mm ² ), the lamp current is I (ampere), and the pressure of the starting rare gas sealed in the arc tube is P.
(Torr), it is characterized by satisfying the following: logP≦0.4 (I/S)+0.9 3.8≦I/S<20. [Embodiment of the Invention] An embodiment of the present invention will be described below based on the drawings. In the figure, 1 is an outer tube, and a neck portion 2 is sealed with a stem 3. A cap 4, which will be described later, is attached to this stem portion. The arc tube 5 housed in the outer tube 1 is made of a translucent ceramic tube, and main electrodes 6a and 6b are disposed opposite each other inside both ends. The arc tube 5 is filled with predetermined amounts of mercury and sodium and a starting rare gas such as xenon gas at a predetermined pressure. The arc tube 5 is supported at both ends by holders 7a and 7b. In this case, one holder 7a is electrically connected to the main electrode 6a, while the other holder 7b supports the main electrode 6b via an insulator 8. The holders 7a and 7b are connected to a support 9 which also serves as a conductive wire, and this support 9 is welded to a well 10 sealed to the stem 3. Note that another well 11 is also sealed to the stem 3, and the other main electrode 6b is connected to this well 11 via an internal lead wire 12. One end of the proximate conductor 13 is freely supported on the one holder 7a, and the proximal conductor 13
The other end is supported by the support 9 via a bimetal piece 14. The proximate conductor is brought into contact with or approached the outer surface of the arc tube 5 before starting the lamp,
After the lamp is lit, the bimetal piece 14 is thermally deformed due to the heat generated by the arc tube 5 and is separated from the arc tube 5. Inside the outer tube 1 is a filament 15 as a starter device.
and a bimetal switch 16 are accommodated. That is, 17 indicates an insulating stand, and this insulating stand 1
A filament 15 is supported by the filament 7 in a planar shape, and a bimetal switch 16 is disposed facing the filament 15.
One end of the filament 15 is connected to the aforementioned internal lead wire 12 via a connecting wire 18, and the other end is connected to one end of a bimetal switch 16. The other end of this bimetal switch 16 is connected to the support 9 via another connection line 19. Therefore, the filament 15 and the bimetal switch 16 form a series circuit as shown in FIG. 2, and this series circuit is connected in parallel to the arc tube 5. Note that the bimetal switch 16 is a normally closed switch. The internal lead wire 12 has a fuse function and is heated to 800°C or higher.
It is made of a conductive wire with a melting point of 2000°C or less, and the cross-sectional area of this conductive wire is S (mm ² ), the lamp current is I (ampere), and the starting rare gas sealed in the arc tube 5 is When the sealing pressure is P (Torr), it is formed to satisfy logP≦0.4 (IL/S)+0.9 and 3.8≦I/S<20. Note that 20 in FIG. 1 is a getter. In addition, a high-pressure sodium lamp with such a configuration has a second
As shown in the figure, Chiyoke coil type ballast 2
It is used by being connected to an AC power supply 22 via 1. The conditions for the internal lead wire 12 having the fuse function were determined through experiments by the inventors, and the experiments will be described below. [Experiment 1] A high pressure sodium lamp with a rated lamp power W _L of 360 watts has a lamp voltage V _L =130 volts and a lamp current I = 3.3 amperes. This lamp is 400
An experiment was conducted in which the ballast was short-circuited when the lamp was lit in combination with a Chiyoke coil type ballast for a Watts mercury lamp. In this case, the following three phenomena occur. (1) The arc tube ruptures from near the electrode tip to the center. (2) The rupture of the arc tube and the melting of the internal lead wire 12 occur simultaneously. (3) Although no rupture of the arc tube is observed, the internal lead wire 12 is fused. If the lamp is directly connected to the power source without using a ballast, the lamp will start due to the high voltage pulse of the starter inside the outer tube due to the inductance component of the power source, but immediately after starting, the above (1) to ( 3) phenomenon occurs. From these experimental results, internal lead wire 1
2 can be melted down faster than the bursting of the arc tube, and this shows that the bursting of the arc tube can be prevented. [Experiment 2] The internal lead wire 12 was made of nickel (Ni), and lamps with various cross-sectional areas S (mm ² ) were made using solid wire or twisted wire, and a test was conducted in which the ballast was short-circuited during stable lighting. The lead wire was fused and the arc tube was ruptured. The results are shown in the table below. The lamps used were 180 watts, 360 watts, and 660 watts compatible with mercury lamp ballasts, all of which were filled with 250 Torr of xenon gas as a starting rare gas.

【table】

[Experiment 3]

In a 360 Watt high pressure sodium lamp similar to [Experiment 1], the xenon gas pressure was set to 50 to 500.
A short-circuit test similar to [Experiment 1] was conducted by varying the torque within the range of (Torr). As a result, it was found that the higher the gas pressure is, the smaller the wire diameter must be in order to prevent the internal lead wire from fusing. The reason for this is that the higher the gas pressure, the faster the gas pressure rises in the arc tube when an overcurrent flows, and therefore it is necessary to melt down the internal lead wire in a shorter time. Then, we further investigated the degree of lead wire fusing by varying the gas pressure with lamps of 180 watts and 660 watts.As with [Experiment 2], we found that the larger the wattage, the thicker the wire diameter remained when the lead wire fused. Ivy. Therefore, using the current density I/S to organize the relationship with the xenon gas pressure P (Torr) in the case where the arc tube does not burst or crack and only the internal lead wires melt, the result is as shown in Figure 3. . The line in FIG. 3 is logP=0.4(I/S)+0.9, and the region below this line produces favorable results. Therefore, in order to melt only the internal lead wire, the relationship between the sealed xenon gas pressure P (Torr) and the current density I/S (ampere/mm ² ) must be regulated to logP≦0.4 (I/S) + 0.9. It turned out to be a good thing. Furthermore, in the embodiment, an example is shown in which the entire internal lead wire has a cross-sectional area that satisfies the above formula, but it is also possible that a part of the internal lead wire has a cross-sectional area that satisfies the above formula. However, the same effect can be obtained if other parts of the internal lead wire have a larger cross-sectional area. The above formula was obtained when the xenon gas pressure was in the range of 50 to 500 Torr, but when the xenon gas pressure is low, the turn-off voltage increases and the lamp efficiency decreases, and conversely, when the xenon gas pressure increases, It is known that the pulse voltage required to start the lamp increases and the startability deteriorates, so it is practically preferable to set the xenon gas pressure in the range of 100 to 350 Torr. Also, even if a mixture of xenon and krypton, neon, and argon is used instead of xenon gas as the starting rare gas sealed in the arc tube, as long as the above equation is met, only the internal lead wires will melt. I confirmed that I would stay. Furthermore, the material of the internal lead wire is not limited to nickel, but may also be iron, copper, aluminum, or materials with additives added to these materials, or alloys thereof, and all of these materials have a melting point of 800.
The temperature is above ℃ and below 2000℃. Those with a melting point exceeding 2000°C are undesirable because they have a large electrical resistivity. Furthermore, if the material has a melting point of less than 800°C, the temperature of the internal parts of the lamp during lamp operation will be around 300°C to 400°C, resulting in a lack of reliability during the lamp's life. In addition, according to the above embodiment, since the internal lead wire with the fuse function is used in place of the conventional internal lead wire for the entire line from the stem to the arc tube, it is similar to the conventional internal lead wire. Assembling is possible through the connection work, reducing the number of work steps compared to replacing only a portion with a fuse, and increasing the connection reliability of the connection points. [Effects of the Invention] As described above, according to the present invention, when an excessive current flows through the lamp, the internal lead wire is fused and the arc tube is prevented from bursting. In particular, the fuse function of the internal lead wire is regulated in relation to the charging pressure of the starting rare gas in the arc tube, so that it does not even cause cracks in the arc tube. Further, according to the conductive wire of the present invention, it does not melt under normal conditions of use and does not deteriorate in practical terms due to oxidation.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; FIG. 1 is a block diagram showing the entire high-pressure sodium lamp, FIG. 2 is a circuit diagram in use, and FIG. 3 is a characteristic diagram. 1... Outer tube, 3... Stem, 4... Cap, 5...
...Earth tube, 6a, 6b...Main electrode, 12...Internal lead wire.

Claims (1)

[Scope of Claims] 1. A high-pressure sodium lamp in which mercury, sodium, and a starting rare gas are sealed in an arc tube made of translucent ceramic, and this arc tube is housed in an outer tube with a cap attached to one end. , at least a part of the internal lead wire introduced from the stem of the outer tube into the outer tube and connected to the arc tube has a temperature of 800°C or higher and 2000°C.
It is composed of a conductive wire with a melting point below ℃, and the cross-sectional area of this conductive wire is S (mm ² ), the lamp current is I (ampere), and the pressure of the starting rare gas sealed in the arc tube is A high-pressure sodium lamp characterized in that, when P (Torr), logP≦0.4 (I/S) + 0.9 3.8≦I/S<20 is satisfied.