JPH09204901A - Double bulb type discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent dust from entering the space between an inner bulb and an outer bulb by a breathing action by the temperature difference between lighting and extinguishment to deteriorate the transparency as in a conventional double bulb type discharge lamp having the inner bulb and the outer bulb sealed with an air passage between the both. SOLUTION: In this discharge lamp 1, an inner bulb 2 and an outer bulb 3 are laid into the state where a rare gas 5 having a gas pressure set to 40-760Torr is present between the both, and sealed so as to have a sealed chamber part 4. Thus, the outer bulb 3 is never damaged, and the breathing action of the sealed chamber 4 with the outside air is eliminated, whereby dust or moisture can be prevented from being penetrated into both the bulbs 2, 3 to reduce the transparency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp such as a mercury lamp or a metal halide lamp, and more particularly to a discharge lamp having a double bulb type inner bulb and outer bulb. Is.

[0002]

2. Description of the Related Art A conventional double bulb type discharge lamp 90 of this type.
FIG. 2 shows an example of the configuration of FIG. 2, in which an inner valve 91 provided with a discharge chamber 91a is provided with an outer valve 92 so as to cover at least a portion of the discharge chamber 91a, and the discharge chamber 91a is exposed to the outside air. It is supposed to prevent excessive cooling due to such reasons as to shorten the starting time.

At this time, it is assumed that air or nitrogen gas exists between the inner valve 91 and the outer valve 92, and these gases expand due to the temperature rise at the time of lighting and the internal pressure rises. In order to prevent the damage of 92, a ventilation passage 93 is provided at the mounting portion of the inner valve 91 and the outer valve 92, for example, by omitting a part of welding.

[0004]

However, in the above-mentioned conventional double bulb type discharge lamp 90, since the ventilation passage 93 is provided between the inner bulb 91 and the outer bulb 92, both bulbs 91, The gas held between 92 expands at the time of lighting and contracts at the time of extinguishing, and by repeating this lighting and extinguishing, the breathing action with the outside is performed through the ventilation passage 93.

Therefore, when the lighting and extinguishing operations are repeated many times, the gas held between the valves 91 and 92 is gradually replaced with the outside air containing dust and humidity, and the dust and the humidity described above cause the outer surface of the inner valve 91 and the outer portion. Valve 92
However, when used as a light source of a headlight, for example, the illuminance is lowered and the light distribution characteristic is changed.

In order to solve the above-mentioned problems, the inner valve 91 and the outer valve 92 are provided without providing the ventilation passage.
However, in this case, the thermal insulation of the discharge chamber 91a against the outside air becomes too high, and the discharge chamber 91a overheats to shorten the life of the double bulb type discharge lamp 90. However, another problem that is caused is caused, and the solution of these points has been a problem.

[0007]

As a concrete means for solving the above-mentioned conventional problems, the present invention provides a dual bulb type discharge lamp in which a bulb is an inner bulb and an outer bulb. The inner valve and the outer valve are sealed as a hermetically sealed state in which a rare gas having a gas pressure of 40 to 760 Torr is present between the inner valve and the outer valve. By providing an electric lamp, the above-mentioned conventional problems are solved.

[0008]

Next, the present invention will be described in detail based on an embodiment shown in the drawings. Reference numeral 1 in FIG. 1 denotes a double bulb type discharge lamp according to the present invention. This double bulb type discharge lamp 1 is composed of an inner bulb 2 having a discharge chamber 2a and an outer bulb 3. This is similar to the conventional example.

Here, in the present invention, the inner valve 2 is used.
The outer valve 3 and the outer valve 3 are sealed without providing a ventilation path, whereby a sealed chamber portion between the inner valve 2 and the outer valve 3 that is not in complete communication with the outside air. 4 will be formed.

The sealed chamber 4 is filled with a rare gas 5 which is a group 0 gas such as helium (He), argon (Ar) and neon (Ne). The filling pressure of the rare gas 5 is determined as appropriate by taking the following conditions into consideration.

First, the first condition for determining the above-mentioned filling pressure is the protection of the outer bulb 3, which is the heat generated when the double bulb discharge lamp 1 is turned on and the expansion of the sealed rare gas 5 causes the outer bulb 3 to expand. The internal pressure is set below atmospheric pressure (760 Torr) so that the valve 3 is not damaged.

The second of the above-mentioned conditions is to secure the thermal conductivity of the rare gas 5, and it is generally said that the thermal conductivity of the gas is not so affected by the pressure. Since the thermal conductivity tends to decrease in a region extremely close to, the thermal conductivity is secured by setting it to 40 Torr or more.

Next, the operation and effect of the double bulb type discharge lamp 1 of the present invention having the above structure will be described. First, first, the inner valve 2 and the outer valve 3 are hermetically sealed to form a hermetically-sealed chamber portion 4, and 40 to 760To is internally provided.
With the configuration in which the rare gas 5 of rr is enclosed, the sealed chamber portion 4 does not perform the breathing action with the outside air, and the outer valve 3 is prevented from being damaged.

At this time, since the rare gas 5 is inactive with respect to the inner valve 2 and the outer valve 3, the outer surface of the inner valve 2 and the inner surface of the outer valve 3 in contact with the rare gas 5 are corroded. It is assumed that the deterioration of the transparency does not occur, and that the transparency of the valves 2 and 3 does not decrease with the lapse of time in combination with the prevention of the respiratory action.

Secondly, the sealed chamber 4 is filled with a rare gas 5 according to the present invention, so that the discharge chamber 2a can be compared with the conventional one filled with the atmosphere or nitrogen gas (N). It was found that the starting voltage in Example 2 markedly decreases, and the variation in the starting voltage also decreases.

That is, with respect to the discharge chamber 2a having a starting voltage of 13 ± 4 Kv when the sealed chamber 4 is filled with the atmosphere or nitrogen gas, the sealed chamber 4 is rarely filled with helium, argon, neon or the like. It has been confirmed by trial production and experiments by the inventor of the present invention that the starting voltage of 6 ± 1 Kv can be reduced even in the same discharge chamber 2a by enclosing the gas 5.

Therefore, in the conventional double bulb type discharge lamp, in order to perform lighting, a power supply device which generates a voltage of at least 17 Kv is required in consideration of the above-mentioned variation, whereas the present invention In the double bulb type discharge lamp 1, the power source device that generates a voltage of 7 Kv is sufficient even if variations are taken into consideration, and the generated voltage is approximately halved.

[0018]

As described above, according to the present invention, a gas pressure of 40 is provided between the inner valve and the outer valve.
First, since the double bulb type discharge lamp in which the inner bulb and the outer bulb are hermetically sealed as the state in which the rare gas of ˜760 Torr is present is present, the outer bulb is damaged. The sealed chamber does not need to breathe with the outside air, and completely prevents dust and humidity from penetrating between the valves to reduce the transparency. It is extremely effective in maintaining the performance of electric lamps.

Secondly, by enclosing a rare gas in the sealed chamber according to the present invention, the starting voltage is remarkably reduced as compared with the conventional encapsulating atmosphere or nitrogen gas. Also, it is possible to reduce the variation in the starting voltage, which enables downsizing and simplification of the power supply device, and also has the excellent effect of improving the handleability of this type of double bulb discharge lamp. It plays.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a double bulb type discharge lamp according to the present invention.

FIG. 2 is a cross-sectional view showing a conventional example.

[Explanation of symbols]

 1 ... Double bulb type discharge lamp 2 ... Inner bulb 2a ... Discharge chamber 3 ... Outer bulb 4 ... Sealed chamber 5 ... Noble gas

Claims (1)

[Claims] 1. A dual bulb type discharge lamp having a bulb composed of an inner bulb and an outer bulb, wherein a gas pressure of 40 to 76 is provided between the inner bulb and the outer bulb.
A double bulb type discharge lamp, wherein the inner bulb and the outer bulb are hermetically sealed in a state where a rare gas of 0 Torr is present.