JPS6353666B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a high-pressure sodium lamp in which an arc tube made of a heat-resistant, alkali-resistant, light-transmitting tube body is mounted inside an outer bulb.

It is well known that high-pressure sodium lamps, in which sodium, mercury, and a starting rare gas are sealed in an arc tube made of translucent ceramic or single-crystalline sapphire, have a higher starting voltage than mercury lamps, fluorescent lamps, etc. It is. For this reason, a thermal starter consisting of a series circuit of a resistor and a bimetal switch is built into the lamp's outer bulb in parallel with the arc tube, and the arc tube is started by the high voltage kick generated when the bimetal switch opens. is used.

By the way, in a lamp with a built-in thermal starter inside the lamp's outer bulb, the thermal starter operates even if the arc tube leaks or does not light up, and the kick voltage is not absorbed by the arc tube and is directly applied to the ballast coil. may be applied to the ballast and damage the ballast.

The present invention eliminates these drawbacks by filling the arc tube with xenon as a starting rare gas, as well as sodium and mercury, and installing a series circuit of a resistor and a bimetal switch in parallel with the arc tube inside the outer bulb of the lamp. In a sodium vapor discharge lamp with a built-in thermal starter, the operating temperature of the resistor of the thermal starter is set to 1,600°C or higher and below the melting point, so that when the arc tube leaks, it is released from the resistor. ionizing the xenon leaked into the lamp's outer bulb by thermionic electrons generated, causing a discharge using the resulting xenon ions as a medium, and melting off the resistor;
This shuts off the thermal starter circuit and stops the starting operation of the faulty lamp.

The present invention will be described in detail below with reference to the drawings. In the figure, numeral 1 is a glass outer bulb whose interior is kept in a high vacuum to obtain desired lamp characteristics. Reference numeral 2 denotes an arc tube made of a translucent ceramic tube body, and ceramic disks 8, 8' to which electrodes 6, 6' filled with emitters made of metal oxide are fixed to both ends are hermetically sealed with a glass sealant. It has been stopped.
Moreover, 7 and 7' are electricity introducing bodies that supply electric power to the electrodes 6 and 6'. In order to start the arc tube 2, a thermal starter consisting of a series circuit of a resistor 3 and a bimetal switch 4 is connected in parallel with the arc tube 2, and a starting auxiliary conductor is connected in the vicinity of the arc tube to facilitate starting. 5 is provided. As an example, 5 mg of sodium, 30 mg of mercury, and 300 torr of xenon gas are sealed inside the arc tube.

In a conventional lamp, when a voltage is applied to the lamp through the ballast, the resistor 3, which is made of a tungsten coil of about 200 ohms, is heated to about 1200°C, and the bimetallic switch 4 is opened by the heat, and at the same time the high voltage generated at this time is The lamp lights up when the voltage is too high. When the lamp is lit, the bimetallic switch 4 is maintained in an open state by the heat of the lit arc tube 2, so that no kick voltage is generated.
However, if there is a leak in the arc tube seal or a crack at the end that occurs at the end of its life, sodium, mercury, and xenon gas will leak into the lamp's outer bulb, causing the lamp to not light or to light at low lamp voltage. However, there are drawbacks such as dielectric breakdown between the internal windings of the ballast due to the kick voltage generated at this time, or overcurrent flowing due to low lamp voltage, which may cause damage to the ballast due to overheating.

In order to eliminate the above drawback, the xenon gas leaked into the outer sphere due to the leakage of the arc tube 2 is discharged.
A test was conducted on a method of cutting off a part of the thermal starter circuit by melting it down using the discharge heat of the xenon ions described above.

Due to the slow leak of arc tube 2, sodium, mercury, and xenon gas leaked into the lamp's outer bulb.
In order to prevent the lamp from remaining lit when the voltage is low, tests have shown that the xenon pressure inside the outer bulb is approximately
I found out that it is best to shut off the thermal starter circuit when the voltage is 0.2 torr. If all the xenon gas instantly leaks into the outer bulb due to a crack in the arc tube 2, the xenon pressure inside the outer bulb will be about 1 Torr, and the Prone to intrabulb xenon gas discharge.

Generally, when metals are heated to high temperatures, they emit thermoelectrons from within the metal, and the present invention takes advantage of this property, using a coiled resistor made of a high-melting point metal such as tungsten, molybdenum, or tantalum. . The temperature of the resistor 3 made of high melting point metal during thermal starter operation can be adjusted by changing the wire diameter and coil length, but the resistance value must be approximately 200 ohms to obtain the specified kick voltage during bimetal operation. It is necessary to do so.

As a result of observing the temperature of the resistor 3 and the xenon gas discharge phenomenon inside the outer bulb during thermal starter operation, if the temperature of the resistor 3 is 1600℃ or higher, the pressure of the xenon gas leaking into the outer bulb is 0.2 Torr or higher. It was found that discharge occurs at This is resistor 3
This is to emit enough thermoelectrons to ionize the xenon gas leaking into the outer sphere and cause an electric discharge when the temperature is 1600°C or higher. It is presumed that when a discharge occurs within the outer sphere, the end of the resistor is bombarded by xenon ions due to the influence of the electric field, resulting in an abnormal temperature rise, leading to fusing. Thermionic emission increases as the temperature of the resistor 3 increases when the thermal starter operates, but since there is a high vacuum inside the outer bulb, it prevents evaporation and disconnection even when the lamp is in normal condition, and provides a sufficient lamp life. In order to guarantee this, the upper limit of the operating temperature is limited by the material of the high melting point metal. It goes without saying that the present invention also includes a case where only a part of the resistor is made of a high melting point metal.

In this way, according to the present invention, there is no need to change the lamp structure or mechanism by simply increasing the temperature of the resistor when the thermal starter operates, and the thermal starter circuit can be reliably shut off, preventing damage to the ballast. This is highly effective in increasing reliability.

[Brief explanation of the drawing]

The figure is a schematic structural diagram of the metal vapor discharge lamp of the present invention. 1... Outer sphere, 2... Arc tube, 3... Resistor, 4
... Bimetal switch, 5 ... Proximity auxiliary conductor,
6, 6'...electrode, 7,7'...current introducing body, 8,
8'... Ceramic disc.

Claims (1)

[Claims] 1. Sodium and mercury are sealed together with xenon as a starting rare gas in an arc tube made of a heat-resistant, light-transmitting insulator, and a resistor made of a high-melting point metal is placed in parallel with the arc tube inside the lamp's outer bulb, which is kept in a vacuum. In a sodium vapor discharge lamp equipped with a built-in thermal starter connected in series with a bimetallic switch, the temperature of at least a portion of the low antibody is set to be 1600°C or higher and lower than the melting point when the thermal starter is operated. A metal vapor discharge lamp characterized in that, when xenon sealed in the arc tube leaks into the lamp outer bulb, the xenon is discharged in the lamp outer bulb and the resistor is fused.