JPH0246648A - Small type metal vapor discharge lamp - Google Patents

Abstract

PURPOSE:To suppress temperature rise of the electrode axis during lighting, as well as to prevent oxidation of an electrode axis, to prevent blackening, so as to improve the maintaining rate of a light beam, by forming an electrode axis part with pure rhenium metal or rhenium-tungsten alloy. CONSTITUTION:An electrode 3 comprises an electrode axis part 4 and an electrode coil part 5 formed in one body by pure rhenium wire. Therefore, the electrode axis part 4 is heated at the time of the squeezing process of a squeezingly sealed part 2, and since rhenium has a high oxidation temperature, a rate of oxidatation is reduced. Accordingly splash of electrode material due to the oxidation may be reduced for peventing the electrode material from sticking to the inner surface of a bulb, and a maintaining rate of a light beam is enhanced. Furthermore, forming of the electrode 3 with rhenium-tungsten alloy provides a higher effect than that formed by conventional pure tungsten or treated tungsten.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a single-sealed small metal vapor discharge lamp that is applied to a small metal halide lamp or the like.

(Prior art) High-intensity discharge lamps, i.e., high-intensity metal vapor discharge lamps (HID), which were traditionally used for outdoor lighting and factory lighting, are now increasingly being used for indoor lighting in stores, etc. It's here.

In particular, metal halide lamps have high efficiency and high color rendering properties, and are therefore suitable for illuminating displayed products, and are becoming increasingly popular.

In this way, in lighting equipment used indoors, it is necessary to reduce the size of the lamp and downsize the entire device including the fixture.

By the way, in general, as lamps become more compact, the shape of the arc tube tends to become closer to an ellipse.

However, for such a small and elliptical arc tube, if the bulb structure is sealed at both ends, which has been commonly used in the past, it not only takes time to mold it, but also the sealing part becomes large, making the shape difficult. However, there are drawbacks such as a large size and an increase in heat loss from the arc tube.

For this reason, consideration has been given to adopting a so-called single-sealed structure in which a pair of electrodes is sealed to one sealed end of this type of small arc tube.

In this way, since there is only one sealing part, the heat loss is smaller than that of a bulb with both ends sealed, which makes it possible to improve the luminous efficiency, and also eliminates the need for molding. Since there is only one sealing portion, which tends to be relatively large compared to the size of the discharge space, there is an advantage that the entire structure can be made smaller.

(Problem WJ to be solved by the invention) However, compared to conventional double-sealed lamps, such single-sealed small metal halide lamps are operated under high lamp load conditions in order to increase luminous efficiency. Ru.

For this reason, lamps are used under harsh conditions, i.e., under high loads where the value of WL/S is about 20 to 70, where the human power is WL (watt) and the inner surface area of the arc tube is S (cm2). It is often lit.

If the lamp is lit under such severe conditions, the arc tube will darken early, the luminous flux maintenance rate will decrease, and the life of the lamp will be shortened.

That is, in this type of lamp, when sealing the pair of electrodes to one sealed end of the arc tube bulb, the electrodes connected to the pair of metal foils are attached to one end of the arc tube bulb made of quartz glass. The bulb is inserted into the open end, and in this state, the open end of the bulb is heated and softened, and then the softened end is crushed. At this time, when two electrodes are inserted into the open end of the bulb, the electrodes are relatively closer to the wall of the arc tube bulb, compared to when one electrode is inserted into the open end of the bulb. Therefore, when the open end of the bulb is heated and softened, the two electrodes are more likely to be exposed to high temperatures and oxidized.

When the electrode is oxidized, the electrode material tends to scatter, and the scattered electrode material adheres to the inner surface of the bulb, which tends to cause blackening. In particular, since this type of lamp has a small arc tube surface area, even a small amount of scattered electrode material causes blackening to progress within a short period of time, resulting in a significant decrease in luminous flux maintenance.

On the other hand, conventional electrodes are made of tungsten (W) or thoriated tungsten, and this type of tungsten has relatively high thermal conductivity, so heat is conducted to the base of the electrode shaft during lighting. Temperatures can easily reach high temperatures.

Moreover, since the bulb is small and single-sealed, the distance between the bases of the electrode shafts in the pair of electrodes is also small, and this causes arc spots to occur between the bases of the electrode shafts, which is related to the high temperature mentioned above. This tends to cause discharge between the bases of the electrode shafts. Such discharge scatters the material on the electrode shaft, leading to breakage of the electrode shaft, which is also a major cause of reduced life.

The first aspect of the present invention is to prevent oxidation of the electrode shaft, and
The purpose of the present invention is to provide a small metal vapor discharge lamp that suppresses temperature rise of the electrode shaft during lighting, prevents blackening, increases luminous flux maintenance rate, and prevents breakage and extends lamp life. .

The second object of the present invention is to provide a small metal vapor discharge lamp that can prevent oxidation of the electrode shaft, prevent blackening, and increase the luminous flux maintenance rate, thereby improving the lamp life.

E Structure of the Invention] (Means for Solving the Problems) The first aspect of the present invention is a single-sealed small metal vapor discharge lamp, in which the electrode has at least the electrode shaft portion made of pure rhenium metal or a rhenium-tungsten alloy. It is characterized by the fact that it has been formed.

The second aspect of the present invention is a single-sealed compact metal vapor discharge lamp, characterized in that the electrode is made of tungsten metal, and the electrode shaft portion is coated with pure rhenium metal or a rhenium-tungsten alloy.

(Function) It is generally said that tungsten (W) oxidizes at about 300 to 500°C, whereas rhenium (Re) is difficult to combine with oxygen until the temperature reaches about 1000°C.

Further, the thermal conductivity of rhenium (Re) (0,095 thermal conductive units) is lower than that of tungsten (W) (0,4 thermal conductive units), and has a high thermal insulation function.

Therefore, according to the first aspect of the present invention, since the electrode shaft portion of the electrode is formed of pure rhenium metal or rhenium-tungsten alloy, it is difficult to oxidize even when heated during sealing.
Therefore, scattering is prevented during lighting, making it difficult to adhere to the tube wall, and blackening is reduced. Furthermore, during lighting, since the thermal conductivity is low, the temperature rise of the electrode shaft portion is suppressed, the generation of electric discharge between the electrode shaft root portions is prevented, and the breakage of the electrode shaft is reduced. For this reason, the luminous flux maintenance rate is increased and the lamp life is improved.

Further, according to the second aspect of the present invention, since the electrode shaft portion is coated with pure rhenium metal or rhenium-tungsten alloy, it is difficult to oxidize even when heated during sealing, and therefore scattering during lighting is prevented and the tube wall It becomes difficult to adhere to the surface, reduces blackening, and increases the luminous flux maintenance rate.

(Example) The first invention will be described below based on the first example shown in FIG.

The drawing shows an arc tube of a metal halide lamp with a lamp power of 150 W. In the drawing, L is an arc tube bulb made of quartz glass, and is formed into a substantially elliptical spherical shape with an internal volume of 0.5 cc.

In such an ellipsoidal bulb l, the long axis direction is the valve axis, and the sealing part 2 is formed at one end in the short axis direction orthogonal to the valve axis. The sealing portion 2 has a flat shape that is crushed and sealed.

Inside the bulb 1, a pair of electrodes 3, 3 are arranged so as to be spaced apart from each other in the axial direction of the bulb, and both of these electrodes 3, 3 are sealed to the crush sealing part 2 on one side.

The electrode 3.3 is composed of an electrode shaft portion 4 and an electrode coil portion 5 for increasing heat capacity. In the case of this embodiment, the electrode shaft portion 4 and the electrode coil portion 5 are made of pure wire with a wire diameter of 0.5 mm. It is integrally formed from rhenium wire. The electrode coil portions 5.5 are opposed to each other at a distance of about 6.8 cm along the valve axis direction, and the electrode shaft portions 4.4 are spaced apart from each other by a distance greater than the distance between the tips of the electrode coil portions 5.5. 6. A metal foil conductor such as Mo or the like sealed to the crush sealing part 2 with dimensions.
6, respectively. The metal foil conductors 6.6 are each connected to an external lead 7.7.

In addition, inside the valve l, there is a starting rare gas, a predetermined amount of mercury, 5n12, NaI, T(l I, Inl.

Metal halides such as NaBr and LiBr are sealed.

In such single-sealed metal halide lamps,
The lamp current I during stable lighting is 1.8A, and the lamp input power W at this time is set to 150W.

In addition, the inner surface area S of the arc tube is 3.58-, and the lamp load per unit surface area of the arc tube is approximately 43 W/c-, so the lamp load is lower than that of a conventional double-sealed metal halide lamp. is almost twice as high.

The operation of the small metal halide lamp having such a configuration will be explained.

In the electrode 3 of this embodiment, since the electrode shaft portion 4 and the electrode coil portion 5 are integrally formed of pure rhenium wire, even if the electrode shaft portion 4 is heated during the crushing process of the crush sealing portion 2, the rhenium wire (Re) has different oxidation temperatures, so the oxidation rate is reduced.

Therefore, the scattering of the electrode material due to oxidation is reduced, the adhesion of the electrode material to the inner surface of the bulb is prevented, and the luminous flux maintenance factor is increased.

Furthermore, since the electrode 3 is made of rhenium (Re), the heat conduction rate is reduced, and a rise in temperature of the electrode shaft portion 4 during lighting is suppressed. Therefore, the arc spot does not move between the root portions of the electrode shaft 4, electric discharge between the electrode shaft root portions is prevented, and breakage due to thinning of the electrode shaft portion 4 is eliminated, resulting in a longer life.

Note that the wire diameter dmm of the electrode shaft portion 4 (including the electrode coil portion 5 in this embodiment) is 2.4≦I/d≦4, assuming that the lamp current during stable lighting of the lamp is ■ ampere. A range of .5 is good.

In other words, when the wire diameter d of the electrode shaft portion 4 becomes thicker, the heat capacity increases, which suppresses the temperature rise of the electrode shaft 4, reduces scattering and thinning of the electrode material, increases the luminous flux maintenance rate, and prevents breakage. Although the life of the lamp will be shortened, if the wire diameter d of the electrode shaft portion 4 becomes too thick, the electrode temperature will drop too much, causing problems such as fading and interfering with the halogen cycle.

For this reason, the inventors' experiments revealed that the wire diameter d (a+a) of the electrode shaft portion 4 and the lamp current during stable lighting
(Ampere) It has been confirmed that the range of 2.4≦I/d≦4.5 is good.

Furthermore, this numerical relationship holds true not only for 150 W metal halide lamps but also for lamps with other rated watts.

In the above embodiment, the case where the electrode 3 was formed of pure rhenium (Re) was explained, but even if the electrode 3 is formed of an alloy of rhenium and tungsten, the electrode 3 is made of pure tungsten or thoriated tungsten. The effect is also recognized.

When such a rhenium-tungsten alloy is used, its mixing ratio (weight ratio) Re/W needs to be 0.05 or more. If the mixing ratio Re/W is less than 0.05, the purpose of using rhenium cannot be achieved, the electrode material tends to scatter and thin, the luminous flux maintenance rate decreases, and the life of the lamp is shortened due to breakage. becomes shorter.

The experimental results that confirmed this point are shown in the table below.

The results in the above table also support that the mixing ratio Re/W of the rhenium-tungsten alloy must be 0.05 or more.

The mixing ratio Re/W is more preferably 0.1 or more, and the upper limit is preferably 0.5 or less.

The reason why the upper limit is 0.5 is that rhenium is expensive, so if it is used in large quantities, it will not only increase the cost, but also that rhenium has good spring properties and is less hard than tungsten, so it is difficult to process, especially at the tip. This is because it becomes difficult to process the coil portion.

Next, a second embodiment of the first invention will be described based on FIG. 2.

In this embodiment, the electrode shaft portion 4 and electrode coil portion 5 of the electrode 3 are formed separately, and the electrode shaft portion 4 has a wire diameter of 0.5 m.
The electrode coil portion 5 is made of pure tungsten or thoriated tungsten with a wire diameter of 0.3.

The electrode coil portion 5 is wound around the bent tip of the electrode shaft portion 4 .

The rest of the structure is the same as that of the embodiment shown in FIG. 1, and the same effects as the first embodiment can be obtained even in this case.

In this case, the wire diameter of the electrode shaft portion 4 is dl(a+m),
When the wire diameter of the electrode coil portion 5 is d2 (mad), it is desirable to satisfy the following relationship: 0.3≦d2 /dl≦1.3.

That is, if the wire diameter of the electrode coil portion 5 becomes too thick,
The heat capacity increases, the temperature becomes less likely to rise, and arc spots are less likely to occur in the electrode coil portion 5. Therefore, stable discharge can be maintained by making the wire diameter of the electrode coil portion 5 1.3 times or less than the wire diameter of the electrode shaft portion 4 and satisfying the relationship 0.3≦d2/di≦1.3. .

In addition, also in the case of the second embodiment, 2.4≦1/d≦4
, 5 is desirable, and rhenium-
When using tungsten alloy, Re/W ratio≧0.
It is desirable to satisfy the relationship 05, and these reasons are the same as those described above.

Thus, from the description of the first and second embodiments, it can be seen that at least the electrode shaft portion 4 of the electrode 3 may be formed of pure rhenium metal or a rhenium-tungsten alloy.

Next, the second invention will be explained based on FIG. 3.

In this embodiment, the electrode 3 has an electrode shaft portion 4 and an electrode coil portion 5 integrally formed, and the electrode shaft portion 4 and the electrode coil portion 5 are made of tungsten or thoriated tungsten.

Note that the electrode may have an electrode shaft portion and an electrode coil portion formed separately as shown in FIG. 2, but even in this case, both the electrode shaft portion 4 and the electrode coil portion 5 are made of tungsten or thoriated tungsten. It is formed.

A straight portion of the electrode shaft portion 4 is covered with a tube 10 made of pure rhenium metal or a rhenium-tungsten alloy.

Other structures may be similar to the first embodiment shown in FIG.

In the case of such a configuration, when sealing the pair of electrodes 3 to one end side of the arc tube bulb l, even if the electrode shaft portion 4 approaches the heated and softened end of the bulb, the electrode shaft portion 4 Since the tube IO made of pure rhenium metal or rhenium-tungsten alloy is coated, the electrode shaft portion 4 made of tungsten is prevented from oxidizing, and since pure rhenium metal or rhenium-tungsten alloy is difficult to oxidize, this tube Oxidation of 10 is also prevented.

Therefore, during lamp lighting, the substances of the electrode shaft portion 4 and tube 10 are less likely to be scattered, the bulb is prevented from darkening, and the luminous flux maintenance rate is improved.

In the case of the second invention, instead of the tube 10, a coating or layer made of pure rhenium metal or a rhenium-tungsten alloy may be formed on the outer surface of the electrode shaft portion 4. The film or layer can be formed by plating, powder application, or the like.

Moreover, it goes without saying that the first invention and the second invention are applied to a lamp that is lit under a high load with a WL/S value of 20 to 70.

Furthermore, both of the above inventions are particularly effective when tin halide (Sn 12 ) is used as the encapsulated halogen, and tin halide promotes the halogen cycle and tends to promote scattering of the electrode material. Application of the present invention is more effective.

Furthermore, the present invention is not limited to the metal halide lamp described in the above embodiments, but may be any discharge lamp in which a crushed seal is formed only at one end of the bulb. It may also be a metal vapor discharge lamp.

[Effects of the Invention] As explained above, according to the first aspect of the present invention, since the electrode shaft portion of the electrode is formed of pure rhenium metal or rhenium-tungsten alloy, it does not oxidize even when heated during sealing. Therefore, scattering during lighting is prevented, making it difficult to adhere to the tube wall, and reducing blackening. Furthermore, during lighting, since the thermal conductivity is low, the temperature rise of the electrode shaft portion is suppressed, the generation of electric discharge between the electrode shaft root portions is prevented, and the breakage of the electrode shaft is reduced. For this reason, even though the single-sealed lamp is operated under a high load with a WL/S value of 20 to 70, the luminous flux maintenance rate is increased and the lamp life is improved.

Further, according to the second aspect of the present invention, since the electrode shaft portion is coated with pure rhenium metal or rhenium-tungsten alloy, it is difficult to oxidize even when heated during sealing, and therefore scattering during lighting is prevented and the tube wall It becomes difficult for the lamp to adhere to the lamp, reducing blackening, and in this case also, the luminous flux maintenance rate increases despite the high load and single-sealed lamp.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a small metal halide lamp showing a first embodiment of the first invention, Fig. 2 is a sectional view of a small metal halide lamp showing a second embodiment of the first invention, and Fig. 3 is a sectional view of a small metal halide lamp showing a second embodiment of the first invention. FIG. 7 is a sectional view of a small metal halide lamp showing an embodiment of the second invention. l... Arc tube bulb, 2... Crushing sealing part, 3...
Electrode, 5... Electrode coil portion, 6... Metal foil conductor, 1
0...Tube.

Claims (2)

[Claims] (1) A crushing seal is formed at one end, a pair of electrodes are sealed to the crushing seal, and a starting rare gas and a luminescent metal are placed inside the arc tube with these electrodes facing each other in the discharge space. and mercury, and the input power is WL (Watt).
, when the inner surface area of the arc tube is S (cm^2), WL
A small single-sealed metal vapor discharge lamp that is lit under a load with a /S value of 20 to 70, characterized in that the electrode has at least an electrode shaft portion formed of pure rhenium metal or a rhenium-tungsten alloy. A small metal vapor discharge lamp. (2) A crushing seal is formed at one end, a pair of electrodes are sealed to the crushing seal, and a starting rare gas and a luminescent metal are placed inside the arc tube with these electrodes facing each other in the discharge space. and mercury, and the input power is WL (Watt).
, when the inner surface area of the arc tube is S (cm^2), WL/
In a single-sealed compact metal vapor discharge lamp that is lit under a load with an S value of 20 to 70, the electrode is made of tungsten metal, and the electrode shaft is coated with pure rhenium metal or a rhenium-tungsten alloy. A small metal vapor discharge lamp characterized by: