JPH10208695A - Metallic vapor discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metallic vapor discharge lamp equipped with an electrode which has equivalent to or more amount of an electron-emissive substance to be held in an electrode than conventional one and has a shorter transfer time from glow discharge to arc discharge and has less scattering of the electron emissive substance. SOLUTION: An electrode shaft 17 is consisted of a tungsten wire with 0.8mm diameter, and a coil which forms 2-layer winding is consisted of an inside coil 15 of 7 turns and an outside coil 16 of 4 turns. The inside coil 15 is consisted of a tungsten wire with 0.3mm diameter, and the outside coil 16 is with 0.1mm diameter. The inside coil 15 is wound closely so that adjoining wires touch each other and the outside coil 16 is wound closely to the inside coil 15 to fill the gap of the inside coil 15. The electron emissive substance 14 is held in space surrounded by inside and outside coils 15 and 16 and the electrode shaft 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal vapor discharge lamp such as a high-pressure sodium lamp, and more particularly to an electrode structure thereof.

[0002]

2. Description of the Related Art FIG. 8 shows a conventional high-pressure sodium lamp. This high-pressure sodium lamp mainly comprises an arc tube 1 and an outer tube having the arc tube 1 provided at one end and containing the arc tube 1. 3 and a pair of support rods 4 and 4 for holding the arc tube 1 in the outer tube 3.

The arc tube 1 is formed in a substantially cylindrical shape by using, for example, a translucent ceramic (polycrystalline alumina, polycrystalline yttria, or the like), which is a translucent member, or single-crystal alumina. An electrode (not shown) provided at the tip of the conductive tube 5 is provided and hermetically sealed. Further, a discharge space, which is an inner space of the hermetically sealed arc tube 1, is filled with xenon gas and sodium as a light emitting substance, and mercury, cadmium, and the like as a buffer gas metal as required.

FIG. 9 shows the structure of a general arc tube and electrodes. The arc tube 1 is a cylindrical shape made of a translucent ceramic, and has a conductive electrode having an electrode 8 fixed to the tip at both ends. A hole for inserting the tube 5 is formed. Xenon gas, sodium and, if necessary, mercury are sealed in the arc tube 1, and niobium (Nb) and 1 with the electrode 8 fixed thereto.
% Zirconium (Zr) conductive tube 5 and arc tube 1
And aluminum oxide (Al ₂ O ₃ )
An arc tube is obtained by fusing with a frit 9 made of yttrium oxide (Y ₂ O ₃ ), strontium oxide (SrO), and calcium oxide (CaO).

FIG. 10 is an enlarged sectional view of an electrode portion. As shown in, for example, JP-A-48-27584, an electrode is generally formed by winding two-layer coils 15 and 16 around an electrode mandrel 17. The emissive material 14 which is turned and reduces the starting voltage is held between the coils 15, 16 and the electrode mandrel 17. However, the electron-emitting substance 14 gradually scatters from the electrodes during the lamp stroke, which blackens the end of the arc tube 1. Due to this blackening, the coldest point temperature of the arc tube 1 increases, and the vapor pressure of the luminescent substance in the arc tube 1 increases. As a result, the lamp voltage rises and eventually causes the lamp to go out.

In order to solve such a problem, Japanese Patent Laid-Open Publication No.
As disclosed in US Pat.
Means 18 for sealing the outer surfaces of the tubes 5 and 16 by welding a hardly soluble metal is used to reduce the scattering of the electron-emitting substance 14 from the coil 16 during the lamp stroke (see FIG. 11).

When the electron-emitting substance 14 disappears,
Since the starting voltage rises and causes the lamp not to light, it is necessary to hold a sufficient amount of the electron-emitting substance 14 on the electrode so that the electron-emitting substance 14 does not disappear during the lamp operation.

Furthermore, the heat capacity of the electrode affects the time required for the arc tube 1 to transition from glow discharge to arc discharge at the start of lighting. Since sputtering is actively performed during the glow discharge, it is effective to reduce the transition time from the glow discharge to the arc discharge in order to suppress blackening of the arc tube 1. For example, JP-A-55-1081
As disclosed in Japanese Patent Application Laid-Open No. 60-260, by setting the inner coil of the two-layer wound coil in the electrode to the multiple wound coil 19 (see FIG. 12), the heat capacity of the electrode is reduced.
As a result, the electrode temperature increases in a short time from the start of lighting, so that the transition time from glow discharge to arc discharge is shortened, and blackening of the arc tube 1 is suppressed.

[0009]

However, in the above conventional example, the scattering of the electron-emitting substance 14 held in the inner coil cannot be completely prevented by the outer coil 16. That is, since the electrode is heated to a high temperature during the lamp stroke, the electron-emitting substance 14 oozes out of the gap between the outer coils 16 and scatters, causing blackening of the arc tube 1 and extinguishing of the lamp. On the other hand, as disclosed in Japanese Patent Application Laid-Open No. 51-48582, if the outer coil 16 is further provided with an electron emitting material scattering prevention means 18, the heat capacity of the electrode becomes large, so that the glow discharge starting from the start of lighting is performed. There is a problem that the time until the transition from the discharge to the arc discharge becomes longer, and as a result, the sputtered amount increases, and the blackening of the arc tube 1 becomes more severe.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. It is an object of the present invention to provide a method in which the amount of an electron-emitting substance held in an electrode is equal to or larger than that of a conventional one, It is an object of the present invention to provide a metal vapor discharge lamp provided with an electrode that has a short transition time to an electrode and has a small scattering of an electron-emitting substance.

[0011]

In order to solve the above-mentioned problems, the present invention provides an electrode structure comprising: a coil portion for holding an electron-emitting substance; and a coil portion provided outside the coil portion. It has electron emission material scattering prevention means to close the gap, and the heat capacity of the electrode is designed so that the transition time from glow discharge to arc discharge at the start of lighting is shorter than that of conventional products It is assumed that.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a metal vapor discharge lamp according to the present invention will be described using a high-pressure sodium lamp as an example.

(Embodiment 1) FIG. 1 is a sectional view showing a first embodiment of an electrode used in the present invention.

First, the structure of a high-pressure sodium lamp to which the electrodes are mounted will be described with reference to FIGS.
The high-pressure sodium lamp mainly includes an arc tube 1 and an outer tube 3 that houses the arc tube 1 and has a base 2 provided at one end.
And a pair of support rods 4 for holding the arc tube 1 in the outer tube 3.
And electrodes 8 provided at the tip of the conductive tube 5 and disposed at both ends of the arc tube 1.

The arc tube 1 has, for example, alkali resistance.
A translucent ceramic that is a translucent member (for example, polycrystalline
Lumina, polycrystalline yttria, etc.) or single-crystalline alumina
Etc., and has an inner diameter of 6 m, for example.
m, the outer diameter is 7.4 mm, and the total length is 60 mm.
In addition, for example, niobium can be seen from the openings at both ends of the arc tube 1.
Conductive tube made of (Nb) and 1% zirconium (Zr)
5 are inserted into the arc tube 1 of the conductive tube 5 respectively.
At the tip on the side, an electrode 8 is formed of aluminum oxide (Al
_TwoO_Three), Yttrium oxide (Y_TwoO_Three), Oxide oxide
From sodium (SrO) and calcium oxide (CaO).
Are respectively bonded to the ends of the arc tube 1 by the frit 9
Thus, the arc tube 1 is hermetically sealed. The arc tube 1
The distance between the electrodes 8, 8 held at both ends of the
The electrode 8 is made of yttrium oxide (Y_TwoO_Three)
Is applied and baked as an electron-emitting substance. So
The discharge space, which is the internal space of the arc tube 1,
Thorium (Na) 5mg, gas pressure 4.0x1 at 25 ° C
0^FourXenon (Xe) of Pa is enclosed.

The outer tube 3 is made of hard glass and has a diameter of 40.
It is formed with a substantially cylindrical space having one end closed and containing the arc tube 1, and a base 2 provided on the other end side and hermetically sealed. A pair of conductive support rods 4 connected to the base 2 provided at the other end are disposed in the substantially cylindrical space.
In addition to supporting the arc tube 1 through the, the inside thereof is evacuated using a barium getter 10 so that the inside of the arc tube becomes a high vacuum. Also, the one support rod 4 is provided with a proximity conductor 11 for applying a predetermined potential and facilitating starting of the lamp so as to extend between the two electrodes 8, 8 substantially along the outer wall of the arc tube 1. One end of the proximity conductor 11 is connected to the support rod 4 via the bimetal 12, so that the proximity conductor 11 does not come into contact with the outer wall of the arc tube 1 while the lamp is lit.

In FIG. 8, reference numeral 13 denotes a connection line for electrically connecting one of the support rods 4 and the conductive tube 5;
The conductive tube 5 on the side where the connection line 13 is provided is attached to the holder 7.
, But is not fixed, and is slidable with the holder 7.

Next, the structure of the electrode mounted on the high-pressure sodium lamp will be described. In FIG. 1, the electrode mandrel 17 is made of a tungsten (W) wire having a diameter of 0.8 mm, and the coil is formed in a double-layered form. The inner coil 15 has seven turns and the outer coil 16 has four turns. The inner coil 15 has a diameter of 0.3 mm, and the outer coil 16 has a diameter of 0.1 mm.
It consists of a tungsten (W) wire having a diameter of mm. The inner coil 15 is wound tightly so that adjacent wires touch each other, but the outer coil 16 is tightly wound around the inner coil 15 so as to close the gap between the inner coils 15. . The electron-emitting substance 14 made of yttrium oxide (Y ₂ O ₃ ) includes inner and outer coils 15 and 16 and an electrode mandrel 17.
It is held in the space surrounded by.

As a comparative example, FIG.
The electrode shown in No. 10 was prepared. The electrode mandrel 17 is 0.8
made of tungsten (W) wire having a diameter of
16 is a tungsten (W) wire having a diameter of 0.3 mm.
The coils 15 and 16 are in the form of a two-layer winding,
15 is 7 turns, and the outer coil 16 is 4 turns. Electric
The pole mandrel 17 projects 2 mm from the inner coil 15.
Yttrium oxide (Y _TwoO_Three) Consisting of an electron-emitting substance
14 is surrounded by inner and outer coils 15 and 16 and an electrode mandrel 17
Is held in a space that is

[0020] Ten high-pressure sodium lamps each having the above-described electrode were manufactured, and these high-pressure sodium lamps were turned on for 5.5 hours and turned off for 0.5 hours using a choke type ballast having a built-in igniter. Lighting evaluation was performed in a blinking cycle. As a result, at the time when the cumulative lighting time reached 5000 hours, it was visually confirmed that the blackening of the arc tube end was more intense in the comparative example. Three lamps out of the ten lamps provided with the electrodes of the comparative example failed to light, but no lamps failed in the lamp provided with the electrodes of the first embodiment.

Further, the increase in the lamp voltage was 3.2 V on average in the first embodiment, and was suppressed from the average of 4.1 V in the comparative example. The transition time from the glow discharge to the arc discharge was 11 seconds on average in Embodiment 1, and 20 seconds on average in the comparative example, which was improved.

(Embodiment 2) FIG. 2 is a sectional view showing a second embodiment of the electrode used in the present invention. This embodiment is characterized in that an outer coil 16 having a smaller diameter than the inner coil 15 is wound tightly so that adjacent wires touch each other. Similarly to 1, the increase in the lamp voltage was suppressed to an average of 2.9 V as compared with the comparative example, and the improvement effect was confirmed such that the transition time from glow discharge to arc discharge was also 12 seconds on average.

(Embodiment 3) FIG. 3 is a sectional view showing a third embodiment of the electrode used in the present invention. In this embodiment, the electrode mandrel 17 is made of a 0.8 mm diameter tungsten (W) wire, the coil 20 is made of a 0.3 mm diameter tungsten (W) wire, and has a seven-turn single-layer winding form. . The electron-emitting substance 14 made of yttrium oxide (Y ₂ O ₃ ) is held in a space surrounded by the coil 20 and the electrode mandrel 17. The outside of the coil 20 is covered with a 0.05 mm thick tungsten (W) cylindrical shielding tube 21.

As described above, the outside of the coil 20 is shielded by the shielding cylinder 2.
In the third embodiment, the electron-emitting substance 14 slightly scatters from the gap between the outer coils 16 in the first embodiment. However, in the third embodiment, the scattering of the electron-emitting substance 14 can be completely suppressed. .

[0025] Ten high-pressure sodium lamps equipped with electrodes according to the present embodiment are turned on for 5.5 hours and turned off for 0.5 hour using a choke-type ballast with a built-in igniter in the same manner as in the previous embodiment. Lighting evaluation was performed in a blinking cycle. As a result, at the time when the cumulative lighting time reached 5000 hours, the blackening of the arc tube end was further improved than in the above-described embodiment, and no unlit lamps occurred.
Also, the rise of the lamp voltage was improved to 2.2 V on average, and the transition time from glow discharge to arc discharge was improved to 14 seconds on average.

When a shield tube similar to the shield tube 21 according to the present embodiment is provided on the outer coil 16 with respect to the conventional electrode shown in FIG. 10, the heat capacity of the electrode is further increased. It was confirmed that the transition time to the arc discharge was as long as 23 seconds on average. This is because the outer surfaces of the coils 15 and 16 shown in FIG.
It is indirectly shown that a similar phenomenon occurs in the means for sealing by welding of No. 8.

(Embodiment 4) FIG. 4 is a sectional view showing a fourth embodiment of the electrode used in the present invention. This embodiment is characterized in that the coil 20 is sparsely wound so as to hold a large amount of the electron-emitting substance 14, and that a shielding cylinder 21 is provided outside the coil 20. In the embodiment, the same effect as in the third embodiment was obtained. That is, when the cumulative lighting time reaches 5000 hours, the increase in the lamp voltage is 2.3 on average.
The transition time from V and glow discharge to arc discharge was also greatly improved, averaging 2 seconds. Further, more electron-emitting substances 14 can be retained as compared with other embodiments,
The rise of the starting voltage can be suppressed low.

In FIG. 4, the coil 20 is wound around the electrode mandrel 17 for four turns.
Even a two-turn coil 20 that only blocks both ends of
It is easily inferred that a similar effect can be obtained.

Since the electron-emitting substance 14 can be held by a shielding cylinder 21 provided outside the coil, the electrode mandrel 17 itself containing the electron-emitting substance 14 as shown in FIG. It is also possible to use a coil 22 having a non-circular cross section as shown in FIGS.

The above embodiments have been described with reference to the case of lighting using a choke type ballast. However, when lighting is performed using an electronic ballast, the constant voltage of the electronic ballast is used. The function further suppresses a rise in the lamp voltage.

It is needless to say that the present invention is not limited to the above embodiments. Further, the same applies to the case where the electrode according to the present invention is used for a metal vapor discharge lamp other than the high-pressure sodium lamp. It goes without saying that the effect is obtained.

[0032]

According to the present invention, as described above, the provision of the means for preventing the scattering of the electron-emitting substance suppresses the scattering of the electron-emitting substance and suppresses the blackening of the end of the arc tube. Rise and disappearance are suppressed. Moreover, since the electrode holds the amount of the electron-emitting substance equal to or more than the conventional amount, the startability during the operation of the lamp becomes equal to or more than the conventional amount. Further, since the electrode heat capacity is equal to or lower than that of the conventional product, the electrode temperature is increased in a short time from the start of lighting, and the transition time from the glow discharge to the arc discharge is shortened, so that the blackening of the arc tube is suppressed. .

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of an electrode used in the present invention.

FIG. 2 is a sectional view showing a second embodiment of an electrode used in the present invention.

FIG. 3 is a sectional view showing a third embodiment of an electrode used in the present invention.

FIG. 4 is a sectional view showing a fourth embodiment of an electrode used in the present invention.

FIG. 5 is a sectional view showing a fourth embodiment of an electrode used in the present invention.

FIG. 6 is a sectional view showing a fourth embodiment of an electrode used in the present invention.

FIG. 7 is a sectional view showing a fourth embodiment of an electrode used in the present invention.

FIG. 8 is a partially cutaway front view showing the high-pressure sodium lamp.

FIG. 9 is a sectional view showing an arc tube.

FIG. 10 is a sectional view showing a conventional electrode.

FIG. 11 is a sectional view showing a conventional electrode.

FIG. 12 is a sectional view showing a conventional electrode.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 arc tube 8 electrode 14 electron-emitting substance 15 inner coil 16 outer coil 17 electrode mandrel

Continued on the front page (72) Inventor Naoki Saito 1048 Odakadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works, Ltd.

Claims (5)

[Claims] 1. A glow at the start of lighting, comprising: a coil section for holding an electron-emitting substance; and an electron-emitting substance scattering prevention means provided outside the coil section and closing at least a gap between the coil sections. A metal vapor discharge lamp comprising an electrode having a heat capacity such that a transition time from discharge to arc discharge is equal to or less than a predetermined value. 2. The metal vapor discharge lamp according to claim 1, wherein said means for preventing the scattering of the electron-emitting substance comprises a coil having a diameter smaller than a diameter of a coil disposed inside thereof. 3. The metal vapor discharge lamp according to claim 1, wherein said electron emission material scattering prevention means comprises a shielding cylinder which covers said coil portion. 4. An inner coil is wound tightly around an electrode mandrel so that adjacent wires touch each other, and an outer coil having a wire diameter smaller than the wire diameter of the inner coil is wound between the wires of the inner coil. A metal vapor discharge lamp comprising an electrode in which an electron-emitting substance is held in a space surrounded by a coil, an outer coil, and an electrode mandrel. 5. An inner coil is wound tightly on an electrode mandrel so that adjacent wires touch each other, and an outer coil having a smaller wire diameter than the inner coil contacts an outer coil of the inner coil. A metal vapor discharge lamp comprising an electrode wound tightly and having an electron-emitting substance held in a space surrounded by the inner coil, the outer coil, and an electrode mandrel.