JPS5818742B2 - High pressure sodium lamp and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION High-pressure sodium lamps using a translucent alumina ceramic tube and containing sodium, mercury, and xenon have come to be widely used for general lighting.

Attempts have also been made to use single crystal alumina tubes, such as sapphire tubes, instead of polycrystalline alumina ceramic tubes.

Enclosed mercury serves as a buffer and serves to increase the potential gradient, xenon is used as a starter, and most of the light emitted by discharge is sodium light.

Conventionally, this kind of lamp, which has become a commercial product, contains more sodium than can be evaporated in the arc tube, and most of the sodium is
This is a so-called saturated vapor pressure type discharge lamp in which IJum is stored together with mercury as surplus amalgam in the coldest part of the arc tube.

For this reason, the sodium vapor pressure within the arc tube varies greatly in response to changes in the temperature of the coldest part, resulting in a drawback in that the lighting characteristics of the lamp vary greatly.

By limiting the amount of sodium sealed and making it a so-called unsaturated vapor pressure type in which all of the sodium is evaporated when the light is on, the pressure inside the tube hardly changes even if the temperature of the coldest part changes, so the lamp does not turn on. It is also already known that the lighting characteristics become extremely stable.

However, the reason why this type of unsaturated vapor pressure type high pressure sodium lamp has not yet been commercialized is because of various technical difficulties.

The reason for these difficulties is that the amount of encapsulation is extremely small.

That is, in the case of a conventional saturated vapor pressure type high-pressure sodium lamp, the amount of enclosed sodium is about 10 to 201n9, whereas in the case of an unsaturated vapor pressure type, the amount of sodium enclosed is <
It is necessary to handle minute amounts of about 1/10■.

Generally, in order to complete a new discharge lamp as a commercial product, the appropriate lamp tube voltage and tube current must be set in consideration of the economic efficiency of the ballast required to turn on the discharge lamp.

In the case of high-pressure sodium lamps, if the arc tube dimensions are constant, the relationship between tube voltage and tube current is determined by the sl-IJ vapor pressure and mercury vapor pressure, and in the case of unsaturated vapor pressure type, the relationship between the filled sodium amount and the Determined by the amount of mercury.

As mentioned above, these amounts are extremely small, and because sodium is an extremely active element that oxidizes quickly in the air, there are technical difficulties in handling it, and it has not been possible to set an appropriate amount for inclusion in the past. .

The inventors completed a prototype lamp by making full use of a filling technique that accurately filled a small amount of substances and completely removed the effects of nitrogen and other impurities, thereby obtaining a relationship curve between the small amount of filling and the lamp characteristics. I was able to set an appropriate amount of inclusion.

In other words, the amount of sodium is 0.018 per 1 d of arc tube internal volume.
m9 to 0.0717Q, and mercury is the same <1 = per 0
．． 054 to 0.536, it was possible to use an economical ballast and to complete a practically suitable unsaturated vapor pressure type high-pressure L-IJ lamp.

The relationship curve between tube current and tube voltage for a high-pressure sodium lamp is as shown in FIG. 1, where curve a is for a conventional saturated vapor pressure discharge lamp, and curve a is for an unsaturated vapor pressure discharge lamp.

In a, the tube voltage increases as the tube current increases, while in b, it is the same as in a while the tube current is small, but when it reaches a certain tube current value, the tube current no longer increases. The curve is such that the tube voltage remains almost constant.

This inflection point C is the point where all the contents in the tube have completely evaporated, and the area to the right of point C indicates an unsaturated vapor pressure type lighting state.

The tube voltage at this time is temporarily called the saturation tube voltage, and for simplicity, V
s employment.

The high-pressure sodium lamp according to the present invention is used in the straight straight section to the right of point C in the rated lighting state, and it is important to appropriately set vsa.

Figure 2 shows the arc tube of the prototype lamp used in the experiment.

The openings at both ends of a translucent alumina tube 1 with an inner diameter of 8 m and a length of 115 mm are sealed with alumina sealing bodies 2, 2', and the external sealing length L1 of niobium exhaust pipes 3, 3' passing through the alumina sealing bodies 2, 2'. 5
mm, and an electrode 4 is connected to the tip of the internal protrusion.

The electrode 4 is made of tungsten and has a coil with an outer diameter of 3.5 mrIL, and the distance L2 between its tip and the inner surface of the sealing body is 6.5 mm.
It was set to 5 mm.

Figure 3 was obtained when the saturation tube voltage Vsa of the lamp with various amounts of sodium and mercury sealed in this arc tube (inner volume about 5.6 alt) was measured.

In FIG. 3A, the horizontal axis represents the amount of enclosed sodium, and the vertical axis represents the value of the saturated tube voltage Vsa.

By the way, in the case of an unsaturated vapor pressure discharge lamp, all of the metal sealed in the arc tube evaporates, so if the amount of enclosed metal is expressed as the amount per unit internal volume of the arc tube, S regardless of the internal volume of the arc tube, This can be generalized as a relationship between the amount of filling and lamp characteristics.

FIG. 3B shows the amount of sodium charged in FIG. 3A divided by the internal volume of the arc tube, 5.6 d, and rewritten as the amount per unit internal volume of the arc tube.

In Figure 3, the straight line d shows the saturation tube voltage and the amount of thorium filled when the amount of mercury filled is constant at 1.0η (0.018 m9/crit per unit internal volume of the arc tube) and the amount of sodium filled is varied. It shows the relationship between

From this figure, it can be seen that when the amount of mercury enclosed is constant, Vsa increases linearly as the amount of Na-IJ increases.

- Conversely, when the amount of mercury was varied while the amount of sodium was constant, the relationship between the amount of mercury and Vsa was as shown in FIG.

In FIG. 4, straight lines e and f are obtained when the amount of sodium enclosed is constant at 0.3 and 0.2, respectively, and it was found that as the amount of mercury increases, Vsa increases exponentially.

Furthermore, the luminous flux of these prototype lamps was measured and the relationship between the amount of sodium filled and the efficiency was determined, and the result shown in FIG. 6 was obtained.

Based on the above test results, the conditions for obtaining an unsaturated vapor positive high pressure sodium lamp with excellent characteristics suitable for general lighting are as follows.

In order to turn on an economical ballast, the tube voltage, that is, the saturated tube voltage V in the case of an unsaturated vapor normal high pressure sodium lamp, is required.
It is preferable that sa is in the range of 80V to 150V, preferably in the range of 100 to 135V.

This is because when Vsa is less than 80V, the lamp current increases and the ballast winding needs to be thicker, making the ballast large and expensive.

Further, if Vsa is 150 .mu. or more, the lamp will turn off and cannot be stably lit using a general high-strength skewer type ballast for a power supply voltage of 2.0 ClV, which is most commonly used.

Furthermore, as a result of experiments, if the amount of sodium is less than 0.01018 m9/d, even if the tube voltage is at a suitable value, there will be almost no monothorium emission, only mercury emission, resulting in poor color rendering; In this case, as shown in FIG. 6, even if the tube voltage is at an appropriate value, the luminous efficiency is poor, and in either case, it is not suitable for general lighting use.

Therefore, taking these into consideration, A, B, C,
The range surrounded by D is practical, and preferably E and F
, G.

This is the range surrounded by H.

In this 5, the range of the amount of mercury enclosed is determined as follows.

In other words, the lower limit of the amount of sodium encapsulated is 0.018~
The upper limit value is the amount of mercury that should make Vsa 150■, the highest value allowed for general lighting at /d, and the upper limit of the amount of sodium filled, which is 0.071■/d, is the maximum value for Vsa for general lighting. 80 is the lowest value allowed
The amount of mercury enclosed that should be V can be considered to be the lower limit.

When these values are calculated from this test data, as is clear from Figure 3, the upper limit of the amount of mercury enclosed is 0.536 m9/c.
rit,, the lower limit is 0.054mt27crit
becomes.

Therefore, from these series of test results, Vsa is 80 to 150.
In order to obtain an unsaturated steam-engineered high-pressure I-IJ lamp that is suitable for general lighting and has excellent efficiency and color rendering properties,
In Figure 3, the amounts of sodium and mercury enclosed are A, B,
It has been found that the range indicated by diagonal lines obtained by connecting points C and D can be used.

By the way, since the quantitative regulation is extremely small as mentioned above, it is impossible to accurately weigh and enclose in the arc tube using normal methods without being affected by the atmosphere.

By utilizing the thermal decomposition reaction of sodium azide (NaN2), the inventors were able to carry out weighing and encapsulation of small amounts for the first time.

t-IJium azide is stable in the air and is extremely easy to handle. By heating it to around 400°C, it causes a decomposition reaction of 2NaN, 2Na + 3N2, and produces high-purity soot. - Separate IJum.

A predetermined amount of sodium azide and mercury are charged into the arc tube or a part communicating with the arc tube, and the interior of the arc tube is made into an inert atmosphere or vacuum, and this part is heated to generate a certain amount of sodium azide. Nitrogen is removed by a vacuum pump.

When inserted into a part communicating with the arc tube, this part is further heated to a high temperature to distill sodium and mercury into the arc tube, and then the unnecessary parts are sealed and fused.

Although this method prevented contamination of the inclusions and achieved some degree of accuracy in weighing, the quantity was still minute, so weighing took time and was insufficient as an industrial production method. .

The inventors added a powder of a refractory substance that does not react with sodium to increase the amount of l-IJium azide, mixed it thoroughly, weighed out a certain amount, and treated it in the same manner as above to prepare Na-IJium. It has been found that the method of encapsulating is appropriate.

That is, since a much larger amount of the mixture was weighed for a given amount of sodium, the time and labor required for weighing were significantly reduced, and the quantitative accuracy was further improved.

In addition, by simultaneously adding mercury to this sodium-resistant refractory material and mixing it, and dispersing the mercury as fine particles throughout the mixture, sodium and mercury can be weighed out at the same time.
Can be enclosed.

An embodiment of the present invention will be explained with reference to FIG.

FIG. 5 shows the same arc tube as shown in FIG. 2 in an unfinished state, and the same reference numerals indicate the same parts.

The planned amount of encapsulation is 0.3 mg of I-IJ and 1.0 mg of mercury. ．． 0
In the case of Tn9, for 100 lights, 85 cm of sodium azide and 100 cm of mercury are mixed with 515 cm of aluminum oxide powder.
Mix thoroughly.

Aluminum oxide powder is used as a mixed material to increase the volume. Any material such as magnesium oxide powder or a suitable metal powder that is sodium-resistant and fire-resistant and stable even at high temperatures may be used. The one that has been applied is better.

7m for one light out of the total of 700m9 of the above mixture
9 is weighed out and charged into the opening of one exhaust pipe 3 of the arc tube shown in FIG.

The mixed charge, indicated at 5 in the figure, may be a suitable compression molded article or may be placed in a refractory container.

After charging the mixed charge, the end of the exhaust pipe 3 is hermetically sealed.

The other end of the exhaust pipe 3' is connected to a vacuum exhaust system, and after creating a high vacuum inside the arc tube, the end of the exhaust pipe 3 is heated to approximately 400°C.
Heat to decompose sodium azide and liberate sodium.

Next, add about 2 xenon from the exhaust pipe 3' connected to the exhaust system.
0 Torr is introduced and the part B is hermetically sealed.

Next, the end of the exhaust pipe 3 is heated to about 700° C. to cause the liberated sodium and mercury to form a groove inside the arc tube.

Since the aluminum oxide mixture remains at the end of the exhaust pipe 3, the exhaust pipe 3 is hermetically sealed at the part A, thereby completing the finished arc tube shown in FIG.

This arc tube is mechanically mounted within a glass outer bulb in the usual manner, and electrical connections are made to complete a lamp that is similar in appearance to a conventional high-pressure sodium lamp.

As a result of lighting this lamp, 12
A saturation tube voltage of 5.5 cm, a tube current of 3.7 A and a tube power of about 400 W were obtained.

Furthermore, the lamp exhibited characteristics of an unsaturated vapor pressure discharge lamp in which the tube voltage remained almost constant even when the tube current was increased.

As described above, the high-pressure sodium lamp according to the present invention has excellent luminous efficiency and color rendering properties, and has a saturation tube voltage of 80 to 150 μ, so it can be lit using an economical ballast and is It has excellent characteristics such as being hardly affected by lighting characteristics.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between tube current and tube voltage of a high-pressure t-IJ lamp, where curve a is for the conventional saturated vapor pressure type, and curve a is for the unsaturated vapor pressure type according to the present invention. It is something. Figure 2 is a partially cutaway front view of the prototype lamp arc tube used in the experiment, Figure 3A is a diagram showing the relationship between the amount of sodium filled and the saturation tube voltage using the amount of mercury filled as a parameter. Figure B is a diagram in which the amounts of sodium and mercury in Figure A are converted into amounts per unit volume in the arc tube, and Figure 4 shows the relationship between the amount of mercury and the saturation tube voltage. Fig. 5 is a cutaway front view of a main part of an unfinished arc tube for explaining the enclosing operation according to an embodiment of the present invention, and Fig. 6 is a diagram showing the relationship between the amount of sodium enclosed and relative efficiency. FIG. 1... Translucent alumina tube, 2. z...Closing body, 3°3'...Exhaust pipe, 4...Electrode, 5...Mixed enclosure.

Claims (1)

[Claims] 1 In metal vapor discharge lamps that utilize sodium luminescence by filling sodium, mercury, and a starting rare gas in a ceramic or single-crystal translucent arc tube, sl-IJium and mercury per 1 d of arc tube internal volume. The enclosed amount is 0.018Tn9 to 0.071■ and 0.53Tn9 respectively.
Within the range of 61n9 to 0.054■, and
- When the amounts of IJ and mercury are selected within the above ranges, the saturation tube voltage is within the range of 80 to 150 cm (within the range surrounded by the four points A, BC, and D in Figure 3). An unsaturated vapor pressure type high-pressure sodium lamp characterized in that a combination of sodium and mercury is selected as shown in the table.