JPH06223775A - Electrode for discharge lamp and its manufacture - Google Patents

Abstract

PURPOSE:To enable temperature to be raised quickly to start lighting by means of a comparatively small input, and concurrently stand sputtering with production cost lowered. CONSTITUTION:A heater 1 composed of a high melting metal in a linear shape is shielded with a high heat resistant insulting film 2, the circumference of which is shielded with sintered material 3 of high melting metallic powder durable against sputtering and electron radioactive material, so as to be combined with a conductive line 4. By this constitution, an electrode for a discharge lamp can be provided, which enables temperature to be raised quickly to start lighting a lamp by means of a comparatively small input, and concurrently stands sputtering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp electrode and a method for manufacturing the same.

[0002]

2. Description of the Related Art In a discharge lamp, especially a low-pressure discharge lamp, a filament electrode as shown in FIG. 12 is used, in which a double or triple coiled tungsten filament 21 is coated with a Ba-based oxide as an electron emitting substance 22. However, the electron emitting substance 22 on the surface is consumed due to the impact (sputtering) of the ionized enclosed gas when the lamp is lit and the evaporation due to the heating of the electrode, which eventually causes the life of the lamp.

The existence of a burning or impregnating electrode is generally known as a material that causes little loss of the electron emissive material. However, these are mainly indirect heating structures, as shown in FIG. That is, since the heater 23 and the impregnated electrode 24 are separated from each other, the heat capacity is large, so that not only a large amount of electric power is required to raise the temperature, but also it takes time. In addition, 25 is a sleeve.

As a means for overcoming these drawbacks, there is a direct heating structure introduced in JP-A-57-121125. This is a cylindrical impregnation electrode 2 as shown in FIG.
A spiral groove is formed on the outer periphery of 4 by a lathe or the like, and the central portion of this cylinder is further cut out, and the spiral outer periphery left after FIG. 14 is used as the cathode.

[0005]

As described above, the direct heating type electrode shown in the present invention has a small heat capacity and can quickly raise the temperature with a small amount of electric power. However, trial production of this results in wasting most of the material of the impregnated electrode, which is uneconomical. As described above, in the conventional invention, it takes either a long time to raise the temperature or the cost is high, which is unsuitable for use in a general lamp.

[0006] The present invention has been made in view of the above points, and is a discharge lamp electrode that is resistant to sputtering and that is inexpensive and that can be heated with a relatively small input sufficient for starting the lamp and a method for manufacturing the same. The purpose is to provide.

[0007]

The present invention is directed to a high melting point metal heater, a high heat resistant insulating film for concentrically covering the heater, a high melting point metal powder for concentrically covering the insulating film, and an electron. It is composed of a sintered body of a radioactive substance and an electric current wire coupled to the sintered body. Further, in claim 2,
A coil-shaped heater with a high melting point metal is coated with a high heat resistant insulating film, and the periphery of the heater is coated with a high melting point metal powder that is resistant to sputtering and a sintered body of an electron emissive material, and the current conductors are joined together for integral molding. It is the one.

[0008]

According to the present invention, the loss of the electron emissive material when the lamp is lit can be suppressed lower than that of the conventional tungsten filament electrode, so that the life of the low-pressure discharge lamp can be extended. . Further, it is possible to provide an electrode for a discharge lamp, which is capable of heating with a relatively small input sufficient for starting the lamp and is inexpensive and resistant to sputtering.

According to the second aspect of the present invention, the temperature rise characteristic is closer to that of the direct heating type, which has better heat conduction than the conventional indirectly heated type impregnated electrode.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. In order to achieve the above object, the present invention, as shown in FIG. 1, coats a linear high melting point metal heater 1 with a high heat resistant insulating film 2 and surrounds it with a high melting point metal powder resistant to sputtering and an electron. The radioactive material sintered body 3 was covered and the conducting wire 4 was connected. As a result, it is characterized as an electrode for a discharge lamp that is sufficiently fast for starting the lamp and resistant to sputtering with an input with a relatively small temperature rise.

As for the size and shape of the electrode according to the present invention, as shown in FIG. 1, the heat conduction equation is analyzed in a concentric model centering on the heater 1 so that the electrode surface temperature can be raised most efficiently. It was decided under the condition that FIG. 2 shows the temperature rise characteristics of the electrode by the analysis, and FIG. 3 shows the comparison between the analysis and the experimental value for the electrode.

The condition required at the time of starting the lamp, that is, the starting condition is 800 to 1000 ° C. one second after the power is turned on. If the shape of the electrode is determined by the analysis, the heat generation amount of the heater satisfying the starting condition can be uniquely obtained. Further, considering the circuit cost, it is necessary to keep the input current as small as possible, so it is understood that it is desirable that the resistance of the heater 1 is high. In this case, a linear heater of Kanthal wire, which has a relatively small temperature dependency of resistance and a relatively large value, was used. The wire diameter of the heater was determined to be between 0.05 and 0.4 mm depending on the balance between heat capacity and strength.

The electricity supplied to the heater 1 must be efficiently converted into heat energy without being short-circuited by the sintered body 3. Therefore, the surface of the heater is covered with the insulating layer 2 having high heat resistance. This time, alumina was coated with a ceramic insulating layer composed mainly of alumina, and the thickness was determined to be 0.2 mm in the direction in which the heat capacity was made as small as possible in the range where insulation could be obtained without short circuit.

The sintered body 3 of the surface layer must hold a sufficient amount of electron emissive material, while the heat capacity cannot be increased so much that the contradictory conditions are required. For this reason, it is difficult to find the optimum value of the thickness of the sintered body 3, but this time it is set to 0.6 mm in consideration of safety. Further, an electric wire 4 is connected to the sintered body 3. With the structure as described above, the electrode according to the present invention has a heat-up characteristic that is better than that of a conventional indirectly heated type impregnated electrode and is closer to that of a direct heating type. Further, as shown in FIG. 2, the results of the analysis show that the electrodes (heater wire diameter: 0.4 mm, insulating layer thickness: 0.2 mm, surface layer thickness:
0.6 mm) supports that it is possible to achieve the starting conditions.

FIG. 3 is a comparison of the temperature rising characteristics of the electrode between the analysis result and the experimental result, and shows a relatively good agreement. When the electrode according to the present invention is used in the discharge lamp, the start is specifically performed by the following procedure. First, before the discharge lamp is turned on, the heater 1 is energized to preheat the sintered body 3 to emit thermoelectrons to trigger a discharge.

Next, if the starting condition is satisfied, main discharge is started and the energization of the heater 1 is stopped. The discharge current flows through the conducting wire 4. After that, the temperature of the electrode is maintained by the lamp current flowing into the cathode (so-called self-heating), and the electron emissive material filled in the pores of the sintered body 3 gradually emits electrons from the portion close to the electrode surface. It evaporates and is lost.

As described above, the supply of electrons is stably performed,
The discharge continues. Moreover, consumption of the electron emissive material due to sputtering or the like at that time is effectively suppressed by the pore structure of the electrode surface. 1A and 1B show the structure of a discharge lamp electrode according to the present invention, wherein FIG. 1A is a plan view and FIG. 1B is a sectional view. In FIG. 1, reference numeral 1 is a heater for electric heating, for example, a tungsten wire, 2 is an insulating film of ceramics or the like covering the outer circumference of the heater, 4 is an electric wire, and 3 is a sintered body of Ba-based oxide and tungsten.

The size and shape of the electrode according to the present invention is the heater 1
By analyzing the heat conduction equation in a concentric model centered on, it is determined under the condition that the electrode surface temperature can be raised most efficiently. FIG. 2 is an analysis result of the temperature rise characteristic of the electrode according to the present invention, and FIG. 3 is a comparison of the analysis result and the experimental result in the temperature rise characteristic.

As described above, the electrode for a discharge lamp according to the present invention can suppress the loss of the electron emissive material when the lamp is lit, as compared with the conventional tungsten filament electrode. Effective in extending the service life. Next, a method for manufacturing the electrode for a discharge lamp of the present invention will be described with reference to FIGS. First, as shown in Figure 4,
A mixed powder 7 is prepared by mixing the electron emissive material 6 and the refractory metal powder 5. Next, the heater 1 having the insulating layer coated thereon is mounted on the pin 9 having the heater-shaped opening 9a as shown in FIG.

The pin 9 is fixed to a jig 10 as shown in FIG. Next, as shown in FIG.
Fill up to the upper surface of No. 1 so that air does not enter evenly and densely. Next, as shown in FIG. 8, a pin 12 having a heater-shaped opening similar to the pin 9 is fixed to the jig 13, inserted into the opening of the jig 11 and lightly pressed. Next, the press is released, and the spacer 14 is pulled out as shown in FIG.

Next, as shown in FIG. 9, the powder is molded by pressing again. Next, as shown in FIG. 10, the jigs 10 and 13 are removed. The molded product remaining inside the jig 11 is inserted into the opening portion of the jig 11 with the spacer 13 sandwiched between the jig 13 having the pins 12 fixed thereto as shown in FIG. By the method described above, the electrode according to the present invention is an indirectly heated type, but it is possible to form an integrally formed structure in which a heater penetrates an electrode different from the conventional one, and the temperature rising characteristic becomes very good.

Next, a specific example of the production of the discharge lamp electrode of the present invention will be described. First, as the electron emitting material 6 in FIG. 4, for example, a mixture of Ba-based oxide and tungsten powder of the refractory metal powder 5 in a weight ratio of 2: 8 is used. The insulating layer coating of the heater 1 is, for example, a tungsten coil (outer diameter: about 0.8 mm, length: with a ceramic coating containing alumina as a main component).
About 17 mm) is used. The molding part is pressed up and down by the surface (diameter: 2 mm) of the tip parts of the jigs 9 and 12, and 20 kgf
2.5mm height of powder by applying pressure up to / cm ^2.
By applying pressure up to 2.5 mm, the powder is compressed to a height of 2.5 mm and molded.

With the above structure, the method of manufacturing an electrode for a discharge lamp according to the present invention has the above-described structure, and thus has a temperature rise similar to that of a direct heating type, which has better heat conduction than the conventional indirectly heated type impregnation electrode. It has characteristics.

[0024]

As described above, the present invention provides a high melting point metal heater, a high heat resistant insulating film that concentrically covers the heater, a high melting point metal powder that concentrically covers the insulating film, and an electron. Since it is composed of a sintered body of a radioactive substance and a current-carrying wire coupled to the sintered body, it is possible to suppress the loss of the electron radioactive substance at the time of lighting the lamp as compared with the conventional tungsten filament electrode. Therefore, there is an effect that the life of the low-pressure discharge lamp can be extended. Further, it is possible to provide an electrode for a discharge lamp, which is capable of heating with a relatively small input sufficient for starting the lamp and is inexpensive and resistant to sputtering.

In the second aspect of the present invention, the coil-shaped high melting point metal heater is covered with a high heat resistant insulating film, and the periphery thereof is covered with a high melting point metal powder resistant to sputtering and a sintered body of an electron emitting substance. Since the current-carrying wires are joined together and integrally molded, the temperature-increasing characteristics are closer to those of the direct heating type and have better heat conduction than the conventional indirectly heated type impregnated electrode.

[Brief description of drawings]

1A and 1B are a side view and a front view of a discharge lamp electrode according to an embodiment of the present invention.

FIG. 2 is a diagram showing an analysis result of temperature rising characteristics of the above electrode.

FIG. 3 is a diagram showing a comparison between an analysis result and an experimental result in the temperature rising characteristic of the same.

FIG. 4 is a process drawing showing the manufacture of the above electrode for a discharge lamp.

FIG. 5 is a process drawing showing the production of the above electrode for a discharge lamp.

FIG. 6 is a process drawing showing the manufacture of the above electrode for a discharge lamp.

FIG. 7 is a process drawing showing the production of the above discharge lamp electrode.

FIG. 8 is a process drawing showing the manufacture of the above electrode for a discharge lamp.

FIG. 9 is a process drawing showing the production of the above electrode for a discharge lamp.

FIG. 10 is a process drawing showing the production of the above electrode for a discharge lamp.

FIG. 11 is a process drawing showing the production of the above electrode for a discharge lamp.

FIG. 12 is a configuration diagram of an electrode of a conventional example.

FIG. 13 is a configuration diagram of another conventional electrode.

FIG. 14 is a configuration diagram of still another conventional example.

[Explanation of symbols]

 1 Heater 2 Insulating film 3 Sintered body 4 Conductive wire

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[Procedure amendment]

[Submission date] May 6, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

The presence of a sintered or impregnated electrode is generally known as a material that causes little loss of the electron emissive material. However, these are mainly indirect heating structures, as shown in FIG. That is, since the heater 23 and the impregnated electrode 24 are separated from each other, the heat capacity is large, so that not only a large amount of electric power is required to raise the temperature, but also it takes time. In addition, 25 is a sleeve.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

Next, a specific example of the production of the discharge lamp electrode of the present invention will be described. First, as the electron emitting material 6 in FIG. 4, for example, a mixture of Ba-based oxide and tungsten powder of the refractory metal powder 5 in a weight ratio of 2: 8 is used. The insulating layer coating of the heater 1 is, for example, a tungsten coil (outer diameter: about 0.8 mm, length: with a ceramic coating containing alumina as a main component).
About 17 mm) is used. The molding part is pressed up and down by the surface (diameter: 2 mm) of the tip parts of the jigs 9 and 12, and 20 kgf
/ Cm ² by applying a pressure to the powder to 2.5mm of
Compress and mold to height .

Claims (2)

[Claims] 1. A high melting point metal heater, a high heat resistant insulating film that concentrically covers the heater, a high melting point metal powder that concentrically covers the insulating film, and a sintered body of an electron emitting substance. An electrode for a discharge lamp, comprising: a current-carrying wire coupled to the sintered body. 2. A coil-shaped heater of a high melting point metal is coated with a high heat resistant insulating film, and the periphery of the heater is coated with a high melting point metal powder resistant to sputtering and a sintered body of an electron emitting material to connect a conducting wire. A method for manufacturing an electrode for a discharge lamp, characterized in that it is integrally molded.