JPH0582018B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a metal halide lamp having a lighting tube for starting the arc tube inside the outer bulb. BACKGROUND OF THE INVENTION In a metal halide lamp, a metal halide, mercury, and a starting rare gas are sealed in an arc tube with electrodes sealed at both ends. Arc tubes are usually made of quartz glass. In such a metal halide lamp, the efficiency and color rendering properties are significantly improved because the metal halide evaporates and dissociates to emit light due to the heat of the arm discharge generated between the two electrodes. However, this metal halide lamp cannot use the barium-based electron-emitting material, which has excellent electron-emitting properties and is generally used in high-pressure mercury lamps, and therefore has a higher starting voltage than high-pressure mercury lamps. Therefore, in order to light the metal halide lamp using a mercury lamp ballast, a structure is adopted in which a lighting tube that generates high-pressure pulses is built into the outer bulb. Problems to be Solved by the Invention However, when the starting of the lamp is ensured by the forced means of incorporating the lighting tube, the starting level of the lighting tube deteriorates to some extent during the movement. The pulse also tends to force the lamp to start, leaving the lamp ready to start for several times the rated life time. On the other hand, the strength of the quartz glass that makes up the arc tube gradually deteriorates due to the long-term high temperatures during its motion, so if it is lit for a period several times its rated life, the operating pressure of the arc tube will drop. If the pressure resistance is below, the arc tube may be damaged. The present invention was made in view of the above circumstances, and the cumulative lighting time of the lamp is 10,000 to 20,000 hours.
To provide a metal halide lamp that stops lighting within a certain period of time. Means for Solving the Problems The metal halide lamp of the present invention has an electrode in a container on at least one side made of a thermally responsive element, and a lighting tube filled with a discharge material mainly composed of helium for pulse generation. Used as an element,
The initial helium gas pressure of the lighting tube is P ₀ (Torr),
The lighting time of the lamp is t (hours), the helium partial pressure after t hours is P (Torr), the average temperature of the lighting tube during lamp lighting is T (℃), and a constant determined by the average temperature T. When K, P=P ₀・e ^-Kt (However, K=3.54016×10 ^-10・T ³ −2.09023×10 ^-7・
T ² +4.23284×10 ^-5・T−2.85853×10 ^-3 A lighting tube in which the initial helium gas pressure and average temperature are determined is provided inside the outer tube. Effect With this configuration, the lighting tube installed inside the outer bulb is heated by the heat from the arc tube and its temperature rises, so that the helium-based discharge electric body sealed inside the lighting tube container is exposed to the wall of the container. permeates and gradually diffuses into the outer tube. As a result, it takes time for the helium partial pressure inside the lighting tube to gradually decrease to 22Torr.
When it reaches 10,000 to 20,000 hours, the lamp stops lighting. Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Figure 1 shows a meral halide lamp according to an embodiment of the present invention, and the lamp rated power is 400W.
General type ballast for high pressure mercury lamps (Chiyoke type)
It lights up with a power supply voltage of 200V.
In the figure, electrodes 2 are sealed at both ends of a quartz arc tube 1 with an inner diameter of 20 mm and a distance between electrodes of 43 mm.
The interior contains scandium, sodium iodide, mercury, and argon gas to aid in starting. The arc tube 1 is held approximately at the center of the outer tube 4 by a stem frame 3. The lighting tube 5 is attached near the stem frame 3 on the base side, and is connected to a current limiting resistor 6.
and a bimetal switch 7 are connected in parallel to both main electrodes of the arc tube 1. The auxiliary electrode 8 is configured such that a potential opposite to that of the adjacent main electrode is applied through an auxiliary resistor 9. As shown in FIG. 3, the lighting tube 5 has an inner diameter of 11.75 mm.
A glass container 9 made of lead glass of mm is provided,
_SiO2 58.5%, _{Al2O3 1.0} %, BaO1.5%, PbO26.5
%, Na ₂ O 8.3%, K ₂ O 4.0%, Sb ₂ O ₃ 0.2%. A stem 12 is attached to the open end of the glass container 9.
is hermetically sealed, and a pair of thermally responsive elements 10 are connected to the tips of two lead wires 13 provided on this stem. Furthermore, thermally responsive element 1
A tungsten contact 11 with a diameter of 0.8 mm and a length of 2.5 mm is welded to the tip of the 0. Inside the lighting tube 5, a mixed gas of 93% helium, 5% hydrogen, and 2% argon is sealed at 58 Torr. The distance of such lighting tube 5 from the center of the luminous tube is 108 mm.
It is installed in the position of Lighting tube 5 in this case
The average temperature while the lamp was on was 200°C. When five lamps having such a structure were lit using the lighting circuit shown in FIG. 3 and a life test was conducted, the lamps failed after 11,000 to 13,200 hours, an average of 12,200 hours. Next, the details of the experiment that led to the completion of the present invention will be explained. First, the inventor used a lighting tube containing 85% or more helium gal inside with the configuration shown in Figure 2.
When we investigated the relationship between the breaking strength of the arc tube and the lighting time, we found that, as shown in Figure 4, for metal halide lamps operating under normal tube wall loads, the breaking strength of the arc tube decreases over a cumulative lighting time of 20,000 hours or more. was found to have decreased to about half of its initial level. Moreover,
Since its breaking strength rapidly decreases around 20,000 hours, lighting for more than 20,000 hours may increase the probability of lamp breakage, which is not preferable. However, the cumulative lighting time of a lamp is generally not controlled, and there are cases where a lamp is used for more than 20,000 hours. On the other hand, typical metal halide lamps typically have a rated life of 9,000 hours, and some low-wattage lamps have a rated life of 6,000 hours. Therefore, even if the lamp becomes defective after 10,000 hours or more, no inconvenience will occur. For these reasons, it is sufficient to cause the lamp to stop lighting within 10,000 to 20,000 hours of accumulated lighting time. When the above-mentioned lighting tube, which is filled with an easily dischargeable electrical substance containing about 85% or more helium, is held in the outer bulb, the temperature of the lighting tube rises due to the heat from the arc tube, and the helium inside the lighting tube increases. Helium passes through the glass container wall and gradually diffuses into the outer tube, and the helium partial pressure inside the lighting tube gradually decreases. The relationship between the helium partial pressure inside the lighting tube and the operating start voltage of the lighting tube (hereinafter referred to as the closed circuit voltage) is as shown in Figure 5.The lighting tube contains an easily discharging electric body containing approximately 85% or more helium. If the helium partial pressure is
At 22Torr, the closed circuit voltage reaches 200V, so the initial helium partial pressure P _{0 (Torr) of the lighting tube and the average temperature of the lighting tube are set so that the helium partial pressure will be 22Torr during the cumulative lighting time of 10,000} to 20,000 hours. By controlling T (°C) it is possible to bring the lamp to failure within that time. The equation that gives the state in which helium gas permeates through the glass container wall is theoretically given by the following equation. P=P ₀・e ^-Kt However, P ₀ : Initial helium gas pressure sealed in the lighting tube (Torr) t : Lamp lighting time (hours) P : Partial pressure of helium gas in the lighting tube after t hours ( Torr) K: Constant The constant K is generally determined by the type of gas, the glass material, and the temperature, but since helium gas is used here, it is constant, and the constant K is also usually determined for the glass material. It has been experimentally confirmed that the glass material has almost no effect on K in the case of soft glass, which is commonly referred to as soft glass. Therefore, the constant K is a constant determined only by the average temperature T (° C.) of the lighting tube during lamp lighting. The relationship between constant K and average temperature T (℃) is
It is given by the following approximate expression from the data of the gas pressure measurement of the lighting tube during the stroke. K=3.54016×10 ^-10・T ³ −2.09023×10 ⁻⁷・T ² +4.23284×10 ⁻⁵・T−2.85853×10 ^-3 Figure 6 shows, for example, helium in a lighting tube with P ₀ = 53.94 Torr. The graph shows the results of calculating the change in partial pressure from the formula P=P ₀ ·e ^-Kt using the average temperature T of the lighting tube as a parameter. The time it takes for P to reach 22 Torr depends largely on the average temperature T of the lighting tube, and from the same figure, for example, when T = 280°C, T
It can be seen that if the temperature is 200℃, it will take approximately 11,800 hours. The average temperature of the lighting tube can vary over a fairly wide range depending on its mounting position within the outer tube. For example, for a lamp that has the same configuration as the 400W metal halide lamp of the above embodiment except for the mounting position of the lighting tube, the lighting tube when the mounting position of the lighting tube is changed into four types as shown in Figure 7. Table 1 shows the relationship between the average temperature and relative distance.

[Table] From Table 1, it can be seen that the average temperature of the lighting tube can be set in various ways by changing the mounting position of the lighting tube within the outer bulb. Figure 8 shows that the initial helium partial pressure P ₀ of the lighting tube is
It shows the change in helium partial pressure during the movement for 50 Torr and 80 Torr. Curves a and c show the case where the helium partial pressure decreases to 22 Torr in 10,000 hours, and curves b and d show the case where the helium partial pressure decreases in 20,000 hours. Each figure shows the case where the partial pressure decreases to 22Torr.
The average temperatures of the lighting tubes corresponding to curves a, b, c, and d can be determined from the above-mentioned formula, and the results are shown in Table 2.

[Table] As can be understood from the above, it is determined by the combination of two variables: the initial helium partial pressure P ₀ of the lighting tube and the average temperature T of the lighting tube, that is, the mounting position of the lighting tube within the outer tube. Accordingly, a desired time (1000 to 2000 hours) for causing the metal halide lamp to malfunction can be set. Effects of the Invention As explained above, the present invention is capable of adjusting the initial helium partial pressure in the lighting tube and the helium partial pressure in the outer tube so that the lamp stops lighting within the cumulative lighting time of 10,000 to 20,000 hours. It is an object of the present invention to provide a metal halide lamp that can prevent lamps from being lit for several times their rated life by specifying the mounting position of the lighting tube, thereby significantly reducing the probability of lamp breakage. It is possible.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway front view of a metal halide lamp which is an embodiment of the present invention, Fig. 2 is a partially cutaway front view of a lighting tube used in the same metal halide lamp, and Fig. 3 is a lighting of the same metal halide lamp. Circuit diagram, Figure 4 is a relationship between the cumulative lighting time of a metal halide lamp and the breakdown strength ratio of the arc tube, Figure 5 is a relationship between the helium partial pressure of the lighting tube and the closed circuit voltage, and Figure 6 is a relationship between the helium partial pressure of the lighting tube and the closed circuit voltage.
The figure shows the change in helium partial pressure with respect to the lamp lighting time using the average temperature of the lighting tube as a parameter.
A diagram plotting the results calculated by P ₀ · e ^-Kt , Figure 7 is a diagram showing the relative position of the lighting tube and arc tube provided in the outer bulb of a metal halide lamp,
FIG. 8 is a diagram showing changes in helium partial pressure during movement when the initial helium partial pressures are 50 Torr and 80 Torr. 1... Arc tube, 2... Electrode, 4... Outer tube, 5...
...Lighting tube, 9...Glass container, 10...Thermoresponsive element.

Claims (1)

[Claims] 1. Using a lighting tube as a pulse generating element, which has an electrode on at least one side of which is a thermally responsive element in a container and is filled with a discharge material mainly composed of helium, the initial helium gas pressure of the lighting tube is is P ₀ (Torr), the lamp lighting time is t (hours), the helium partial pressure after t hours is P (Torr), the average temperature of the lighting tube while the lamp is lit is T (℃), and the average temperature When K is a constant determined by T, P
=P ₀・e ^-Kt (However, K=3.54016×10 ^-10・T ³ −
2.09023×10 ^-7・T ² +4.23284×10 ^-5・T−2.85853
×10 ^-3 ) Helium partial pressure P given by the formula
However, the time it takes to drop to 22Torr is ~10,000 hours
A metal hyride lamp, characterized in that a lighting tube is provided in the outer bulb, with the initial helium gas pressure and the average temperature determined so as to last within 20,000 hours.