JPH0244448Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a metal vapor discharge lamp having an arc tube made of translucent ceramics, such as polycrystalline alumina ceramics or metal oxide single crystals such as sapphire. .

[Technical background of the invention and its problems]

In a metal vapor discharge lamp, such as a high-pressure sodium lamp, which has an arc tube made of a translucent ceramic tube, mercury and sodium are sealed together with a starting rare gas in the arc tube. As the starting rare gas, xenon Xe is usually used because it has low thermal conduction loss and can therefore increase luminous efficiency.
However, unlike argon, etc., Xe does not produce the Penning effect, so the starting voltage of the arc tube is high, making it impossible to start with commercial power supply voltage, and requiring an expensive dedicated starting device that generates high-voltage pulses. needed a device. In contrast, a starting device consisting of a series circuit (thermal response switch and coil filament) or (thermal response switch, heating coil filament, and current limiting resistor) is housed in parallel with the arc tube in an outer tube kept in a high vacuum. Furthermore, in order to lower the starting voltage, a lamp was developed that was able to be lit using an inexpensive mercury lamp ballast by attaching a starting auxiliary conductor (proximity conductor) close to the outer wall of the arc tube. By the way, in such a lamp, if the gas inside the arc tube were to leak (this may occur, for example, at the end of its life), the Xe sealed inside the arc tube would be removed from the outer bulb, which is kept in a high vacuum. , mercury and sodium leak.
If the power switch is turned on when the gas pressure of Xe leaking into the outer tube is 0.1 torr or more in such a state, the starting device is activated and generates a pulse, which may cause the arc tube to light up. in this case,
Since a large amount of mercury sealed in the arc tube leaks into the outer bulb, the lamp voltage does not increase, and therefore a current almost as high as that of shorting the secondary side flows through the ballast, causing burnout of the ballast. There was a risk that this would occur.

To address these shortcomings, for example,
-122351 Publication states that the temperature of the starting device resistor (coil filament) installed in parallel with the arc tube is kept at a high temperature of 1600°C or higher during operation, and in the event that the gas inside the arc tube leaks, Xe is released inside the outer bulb. When 0.2 Torr or more leaks, a method has been shown in which Xe is ionized by thermionic electrons emitted from the resistor (coil filament) to generate a discharge inside the outer tube and fuse the resistor (coil filament). If the Xe gas pressure leaking from the arc tube into the outer tube is as low as, for example, 0.1 Torr, the arc tube may turn on without the coil filament melting, which may burn out the ballast. Furthermore, in Japanese Patent Application Laid-Open No. 55-124941, BaO,
When an electron radioactive substance such as ZnO or SrO is coated and the arc tube leaks and more than 0.2 Torr of Xe leaks into the outer tube, heat is released from the resistor (coil filament) set at 1000℃ to 1400℃. A method of ionizing Xe with electrons to generate a discharge inside the outer bulb and fusing the resistor (coil filament) has also been shown, but in this case, the electron radioactive material coated on the resistor (coil filament) It heats up and scatters every time it is started, and this phenomenon becomes more severe as the lighting time passes, and when a critical gas leak occurs in the arc tube, which tends to occur at the end of a lamp's life, most of the applied amount is scattered. It was useless, and sometimes the resistor (coil filament) could not be fused.

Furthermore, both of the above methods involve arc discharge when the filament is fused, but one pole of this discharge is likely to emit thermoelectrons due to the heated filament, while the other pole is heated by the filament. Since it is a non-heating object such as a response switch or a support wire, the arc discharge becomes a half-wave discharge, or direct current discharge, with only the coil side as the electron emission source, and the current limiting effect of the ballast hardly works, causing an excessive Current will flow. As a result, the overcurrent circuit breaker activates, causing other normal lamps connected to the same circuit to go out at the same time, leaving the entire illuminated area in darkness, creating an extremely dangerous situation. The insulation of the ballast could also be damaged.

[Purpose of invention]

The present invention has been developed to address the above-mentioned drawbacks of the conventional art, and is designed to ensure that the coil filament of the starting device is melted when the lamp is started with the gas inside the arc tube leaking into the outer bulb. Therefore, it is an object of the present invention to provide a metal vapor discharge lamp in which the ballast can be prevented from burning out.

[Summary of the idea]

The present invention is a metal vapor discharge lamp in which a starting device consisting of a thermally responsive switch and a coil filament is sealed together with an arc tube in an outer bulb. By forming the coil filament, the coil filament is reliably fused when starting with the gas sealed in the arc tube leaking into the outer bulb.

[Example of idea]

Hereinafter, details of the present invention will be explained with reference to the illustrated embodiments. FIG. 1 is a front view of a high-pressure sodium lamp which is an embodiment of the present invention, FIG. 2 is an enlarged view of the main parts thereof, and FIG. 3 is a lighting circuit diagram thereof. 1 in the figure maintains a high vacuum inside.
An outer tube 3 has a cap 2 attached to one end, and 3 is a light emitting tube made of translucent ceramic.For example, the both ends of the translucent alumina ceramic tube 4 are coated with adhesive such as glass solder by closing bodies 6a and 6b that support electrodes 5a and 5b. It is hermetically sealed via a , and inside it, a rare starting gas, xenon Xe, and a luminescent substance, sodium ammalgam, are sealed. Reference numeral 7 denotes a starting device which is electrically connected in parallel with the arc tube 3 and includes a bimetal 8 and contacts 9a and 9 for generating high voltage pulses for starting.
The switch 10 is made up of a thermally responsive switch 10 and a coil filament 11 connected in series to the thermally responsive switch 10, and is mounted on a heat-resistant substrate 12. If necessary, a current limiting resistor (not shown) may be further added to the starting device 7. 13 is a nearby conductor for starting assistance,
It is connected to the arc tube support 14 which also serves as a power supply to the one electrode 5a, and is provided along the outer surface of the arc tube 3 in close proximity to the other electrode 5b having a counter potential. A getter 15 is used to maintain the inside of the outer tube 1 at a high degree of vacuum.

More specifically, the starting device 7, which is the main part, will be described in detail. As shown in FIG.
etc., and attached to the heat-resistant substrate 12. One end 11 of the coil filament 11
a is connected to the internal lead-in line 19 via the feeder line 18, while the other end 11b is connected in series to the bimetal 8 via the feeder line 20 and the contact 9b, and one end of the bimetal 8 is connected via the feeder line 21 to the bimetal 8. It is connected to an arc tube support 14 that also serves as a power supply. Moreover, the important point is that the coil filament of the conventional lamp shown in Fig. 1 is formed in a substantially straight line when viewed from above.
In contrast, the coil filament 11 of this embodiment is formed in a substantially U-shape, and the opposite ends 11a and 1 are applied with opposing potentials.
By arranging the electrodes 1b very close to each other and facing each other with a distance of about 10 mm or less, a higher opposing potential is applied.

When a lamp with such a configuration is connected to an AC power source 23 via a single-yoke type mercury lamp ballast 22 for a 200V class AC power source as shown in Fig. 3, the thermally responsive switch 10 closes before the lamp starts. Because of this, the coil filament 11 is energized and generates heat, and this heat causes the thermally responsive switch 10 to open. This kick voltage at the time of opening generates a high voltage pulse in the ballast 22, and this high voltage pulse is applied to both electrodes 5a, 5b of the arc tube 3 to start the lamp.
At this time, since the proximal conductor 13 is close to the outer surface of the arc tube 3, the application of the high voltage pulse causes a rapid potential gradient between it and the electrode 5b on the opposite potential side, and the inside of the arc tube 3 is Promotes the occurrence of arc discharge.

On the other hand, arc tube 3 has leaked and is filled with substances inside the tube.
When the coil filament 11 is electrically heated with Xe etc. leaking into the outer tube 1, thermoelectrons are emitted from the coil filament 11, and the thermoelectrons are accelerated by the voltage applied to the coil filament 11 and are arc discharge occurs by ionizing the Xe gas. At this time, both ends 1 of the coil filament 11 which is in a high temperature state are exposed to a high opposing potential.
Since 1a and 11b are placed very close together as described above, thermionic electrons in this part are accelerated at the highest voltage, and both ends 11a and 11b act as hot cathodes. This causes a bright spot of arc discharge, leading to instant disconnection. In this way, compared to conventional lamps where the ends of the coil filament are separated by a large distance, the coil filament is formed in a shape that is much more likely to cause wire breakage, so the lower Xe gas pressure that could not cause wire breakage in conventional lamps However, disconnection can occur easily enough. Moreover, there is no need for any special additional means to facilitate discharge, such as the combined use of an electron radioactive substance, and in addition, both ends 11 of the coil filament 11, which become arc bright spots when the entire coil filament 11 is in a high temperature state, are not required.
Since a and 11b are also high-temperature hot cathodes, there is no half-wave discharge, that is, direct current discharge, and therefore the current-limiting effect of the ballast 22 as in the conventional case hardly works, and an excessive current flows and the ballast is damaged. Accidents such as breakdown of insulation can also be prevented.

In the above embodiment, the shape of the coil filament 11 is U-shaped, but it is not limited to this shape, and may be, for example, a curved arc. In short, the coil filament 11 should have a shape in which both ends, to which a high counter potential is applied, are close to each other and face each other. It is sufficient if it is formed. In addition to being attached to the heat-resistant substrate 12 using anchors 16, clamps 17, etc., the coil filament 11 may be wound around a heat-resistant cylinder, for example.

In addition, the starting rare gas is not just Xe, but also a mixture of Xe as the main ingredient and other rare gases such as Ne and Ar in an amount of about 10% or less, and other metals other than sodium mentioned above and other metals as luminescent substances. There is no problem with the use of halides.

[Effect of idea]

As detailed above, according to the present invention, the two ends of the coil filament for the starter, to which a high opposing potential is applied, are formed in a shape that closely opposes each other, so that the gas sealed inside the arc tube leaks and leaks into the outer tube. By reliably melting the coil filament when starting under such conditions, the starting circuit can be opened and damage to the ballast can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a front view of a high-pressure sodium lamp which is an embodiment of the present invention, FIG. 2 is an enlarged view of the main parts thereof, and FIG. 3 is a lighting circuit diagram of the lamp. 1... Outer tube, 3... Arc tube, 5a, 5b... Electrode, 7... Starting device, 8... Bimetal, 9a,
9b... Bimetal contact, 10... Thermal response switch, 11... Coil filament, 11a, 11
b...Coil filament end, 13...Proximity conductor.

Claims (1)

[Scope of utility model registration request] An arc tube consisting of a translucent ceramic tube with a pair of opposing electrodes at both ends and xenon gas, mercury, and a luminescent substance sealed inside, and a thermally responsive switch and coil electrically connected in parallel with the arc tube. 1. A metal vapor discharge lamp in which a starter device consisting of a series circuit of filaments is housed in an outer bulb, characterized in that the coil filament is formed in such a shape that both ends thereof are closely opposed to each other.