JPH11307056A - Tubular bulb closing part structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a leak in lighting a lamp by forming with almost column functionally gradient materials whose one side is a non-conductive region and other side is a conductive region, constituting the end part of the non-conductive region with mainly alumina, and including a non-conductive inorganic material component having lower melting point than alumina in the region where a conductive material component is mixed to the alumina. SOLUTION: The end part of a closing tube 12 connected to an arc tube 11 is sealed with a closing part structure 40, an electrode core rod 30 of an electrode 20 is made of a tungsten rod, and fixed by the sintering of the closing part structure 40. A non-conductive region side end surface 41 of the closing part structure 40 is a layer of only a non-conductive inorganic material component whose main component is alumina, and the concentration of a conductive inorganic material component such as tungsten is gradually increased toward a conductive region side end surface 42 to form a multiple layer. As a second non-conductive inorganic material component having a melting point lower than alumina, silica is added. Thereby, generation of cracks in sintering is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bulb closing structure for closing a closed tube connected to an alumina arc tube.

[0002]

2. Description of the Related Art A bulb, for example, a discharge lamp has a bulb generally made of quartz glass, and a pair of electrodes are arranged in a spherical or elliptical arc tube to face each other. A discharge gas or the like is sealed. And
A cylindrical occlusion tube is connected to the end of the arc tube. The occlusion tube has an electrode core rod having an electrode at a tip thereof fixed to a central hole of the occlusion structure. Is closed. Here, since the electrode core rod made of tungsten and the closed portion made of quartz glass have a large difference in thermal expansion coefficient, it is not possible to close the closed tube by directly welding the closed tube to the electrode core bar.

[0003] For this reason, conventionally, the sealing was performed by a foil sealing method or a step joint method, but recently, a functionally graded material formed of a non-conductive inorganic material component such as silica and a conductive inorganic material component such as molybdenum. Attention has been focused on closing an obstruction tube at the end of an arc tube with an obstruction portion structure formed in a substantially columnar shape by a sintering method. The closed portion structure formed of such a functionally graded material has a non-conductive component such as silica rich at one end, and the ratio of a conductive component such as molybdenum continuously increases toward the other end. Or incrementally. Therefore, in the case of a functionally graded material formed of silica powder and molybdenum powder, the vicinity of one end of the closed part structure is non-conductive and has a coefficient of thermal expansion close to that of quartz glass, and during welding, It fits well with a quartz glass closed tube. The vicinity of the other end is electrically conductive and has a characteristic that the coefficient of thermal expansion is close to that of molybdenum.

[0004] When molding a closed structure using a functionally gradient material composed of a conductive inorganic material component and a non-conductive inorganic material component, first, a binder is added to these powders whose mixing ratios are sequentially changed, and a powder is mixed. A powder body is prepared, and the powder mixture is pressed in a mold to obtain a substantially cylindrical pressure-formed body.
Then, the press-formed body is temporarily sintered to obtain a temporarily sintered body. next,
A hole is formed in the axis of the pre-sintered body so as to embed the electrode core rod, thereby forming a central hole. Alternatively, it is pressed in a mold having a protruding member for forming a center hole to obtain a press-formed body in which a center hole is formed in advance, and this is temporarily sintered. And
An electrode core rod integrated with an electrode made of, for example, tungsten is inserted into the center hole of the temporary sintered body at the end thereof, and then the main body is sintered. The temperature of the main sintering is about 1700 ° C. when the non-conductive inorganic substance component is silica.

[0005]

By the way, in the case of a metal halide lamp, for example, depending on the type of metal halide to be sealed, if the bulb is formed of quartz glass,
Since the metal vapor easily reacts with the quartz glass at the time of lighting, the bulb may be formed of alumina which does not easily react with the metal vapor. In addition, the sealing portion is required to be small in size and low in cost. In this regard, it is preferable that the sealing portion is sealed with a closing portion structure made of a functionally gradient material. Therefore, when the valve is made of alumina, the closing portion structure for sealing the closing tube uses a functionally gradient material whose non-conductive inorganic substance component is alumina of the same material as the valve.

However, since the melting point of alumina is higher than that of silica, it is necessary to perform sintering at a high temperature of 1900 ° C. or more when fully sintering a functionally gradient material in which the non-conductive inorganic substance component is alumina. That is, it is necessary to sinter at a higher temperature than 200 ° C. as compared with the case where the non-conductive inorganic substance component is silica. For this reason, the heaters of the electric furnace for sintering are greatly consumed, which is not practical. Therefore, it is desirable to sinter at the lowest possible temperature, but if the non-conductive inorganic material component is alumina, the functionally graded material is finally sintered at a temperature of about 1700 ° C. Cracks occur in the damaged area, and the airtightness is reduced. In addition, the end portion of the non-conductive region made of only alumina is insufficiently sintered, so that the airtightness is reduced and the lamp leaks when the lamp is turned on.

Accordingly, the present invention provides a high airtightness even when a non-conductive inorganic material component is alumina at which a functionally graded material is alumina at a low temperature, and has a blockage of a lamp tube which does not leak when the lamp is turned on. It is intended to provide a partial structure.

[0008]

In order to achieve this object, the present invention provides a conductive inorganic material component and a non-conductive inorganic material component having a stepwise concentration gradient in the longitudinal direction, and one of the conductive inorganic material component and the non-conductive inorganic material component having a non-conductive concentration gradient. In a closed portion structure of a bulb for sealing a closed tube connected to an alumina arc tube, which is made of a substantially columnar functionally graded material that is a conductive region and the other is a conductive region, The main component of the inorganic substance component is alumina, and the end on the non-conductive region side is formed of a layer of only a non-conductive inorganic substance component containing alumina as a main component. A region where the conductive inorganic material component is mixed with the inorganic material component contains a second non-conductive inorganic material component having a lower melting point than alumina. As the second non-conductive inorganic substance component, silica or glass containing silica as a main component is preferable.

[0009]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 shows a metal halide lamp having a rated power consumption of 20 W in which a closed tube 12 of a valve 10 made of alumina is closed by a closed structure 40 made of a functionally graded material. In FIG. 1, a pair of electrodes 20 made of tungsten are opposed to each other inside an arc tube 11 at the center of a bulb 10. Further, a metal component and a halogen are sealed inside the arc tube 11. Examples of the metal component include dysprosium, indium, and tin. The closed tubes 12, 1 are provided at both ends of the arc tube 11, respectively.
2 are connected in series, and the ends of the closed pipes 12 and 12 are sealed with a closed structure 40. Electrode core 30 of electrode 20
Is made of a tungsten rod, is embedded in an axial central hole 43 formed in the closing portion structure 40, and is fixed by baking by sintering. Then, the end of the closing tube 12 is fitted into the concave portion 44 formed in the non-conductive region side end surface 41 of the closing portion structure 40, for example, SiO ₂ —Al ₂ O ₃ −
Are sealed welded sealed at a frit 50 made of _{Dy 2 O 3 -La 2 O 3} .

The closed part structure 40 is a sintered body of a functionally gradient material composed of a conductive inorganic material component such as tungsten or molybdenum and a non-conductive inorganic material component mainly composed of alumina. Non-conductive area side end face 41 of closing part structure 40
Is a layer of only a non-conductive inorganic material component mainly composed of alumina in which tungsten or molybdenum, which is a conductive inorganic material component, is not mixed, and the concentration of the conductive inorganic material component sequentially toward the conductive region side end face 42. Is a multilayer body in which layers with increased numbers are laminated. And the second melting point lower than alumina
Silica is added as a non-conductive inorganic substance component. As the second non-conductive inorganic component having a lower melting point than alumina, alumina silicate glass, alumina borosilicate glass, borosilicate glass, or the like can be used in addition to silica.

As described above, since the second non-conductive inorganic substance component having a lower melting point than alumina is added, when such a functionally gradient material is fully sintered to form the closed structure 40,
Even if the sintering temperature is, for example, about 1700 ° C., no crack is generated during sintering, and the degree of sintering is sufficiently advanced to improve airtightness. Therefore, the closed part structure 40
When the lamp is turned on, the high-pressure gas in the arc tube 11 does not leak when the bulb is closed.

[0012]

Next, a description will be given of an embodiment in which a closed structure 40 is actually manufactured, and a leak state when a metal halide lamp in which the closed tube 12 is closed by the closed structure 40 is turned on is investigated.

[First Embodiment] An example in which the closing structure 40 is made of an alumina-tungsten functionally gradient material will be described. First, an alumina powder having an average particle diameter of 0.4 μm and 1 μm
Silica powder having an average particle size of 5.6 μm was further added to the mixed powder obtained by changing the mixing ratio of the tungsten powder of m, thereby preparing six types of mixed powder bodies. Table 1 shows the mixing ratios of the six types of mixed powders of the alumina powder, the tungsten powder, and the silica powder and the layer thickness during sintering.

[Table 1]

An organic binder, for example, a solution of stearic acid was mixed with these mixed powders in an amount of 5 wt%. This mixture was filled into a cylindrical mold having protruding members for the center hole 43 and the concave portion 44 so that the mixing ratio of alumina and tungsten was sequentially changed, that is, in the order of the layer numbers in Table 1. Then, from the outside of the cylindrical mold, 1.0 to 1.5
By applying a pressure of ton / cm ² , a substantially cylindrical pressure-formed body having a center hole formed therein was obtained. Next, the obtained pressure-molded body was sintered at 1200 ° C. for 30 minutes in a non-oxidizing atmosphere to remove an organic binder to obtain a temporarily sintered body.

The electrode core 30 was inserted into the center hole of the pre-sintered body, and main-sintered at 1700 ° C. for 10 minutes in a non-oxidizing atmosphere. As a result, the electrode core rod 30 is
The sintering temperature of 1700 ° C. is the same as the sintering temperature of the silica-tungsten functionally gradient material, and the sintering electric furnace is used. It is practical because it consumes less heaters.
And, despite the low sintering temperature, no crack occurred in the closed part structure 40. The end of the closed tube 12 was fitted into the concave portion 44 formed on the non-conductive region side end surface 41 of the closed portion structure 40, and was welded and sealed with the frit 50 to produce a metal halide lamp. Then, when the metal halide lamp was turned on, the high-pressure gas in the arc tube 11 did not leak, and the lamp operated normally.

Example 2 A closed part structure 40 was manufactured from an alumina-molybdenum functionally graded material. First, silica powder having an average particle size of 5.6 μm was added to a mixed powder obtained by changing the mixing ratio of alumina powder having an average particle size of 0.4 μm and molybdenum powder having a particle size of 1 μm. Then, six kinds of mixed powder bodies were prepared. Table 2 shows the mixing ratio of the alumina powder, molybdenum powder, and silica powder of the six types of mixed powders and the layer thickness during sintering.

[Table 2]

Next, in the same manner as in Example 1, a pressed compact was obtained from the mixed powder, and a temporary sintered body was obtained from the pressed compact. The pre-sintered body was fully sintered at 1700 ° C. for 10 minutes in a vacuum of 10 ⁻³ Pa or less. In this case as well, no cracks occurred in the closed part structure 40, and during lighting, the high-pressure gas in the arc tube 11 did not leak, and it operated normally.

[Embodiment 3] In Embodiment 1 described above,
Although 5 vol% of silica was uniformly added to each layer of the functionally graded material, in this example, as shown in Table 3, silica was added to the layer of layer number 1 made of alumina alone without mixing tungsten. Without addition, silica was added to a layer in which tungsten was mixed with alumina to prepare six types of mixed powders. The concave portion 44 of the closed portion structure 40 to which the end of the closed tube 12 is connected is formed in the layer of layer number 1 made of only alumina.

[Table 3]

In this embodiment, a mixed powder, a press-formed body, and a pre-sintered body are formed in the same manner as in the first embodiment, and the pre-sintered body is heated at 1750 ° C. in a non-oxidizing atmosphere.
Main sintering for minutes. That is, the main sintering was performed at a temperature higher by 50 ° C. than the main sintering temperature in Examples 1 and 2. As a result, no cracks occur in the obtained closed part structure 40, the airtightness is sufficient, and the light emitting tube 11
The high-pressure gas inside did not leak and operated normally. And
Even if the main sintering is performed at 1750 ° C., the layer made of only alumina is covered with the frit 50, so that no leak occurs. Is much lower, and the heater of the electric furnace for sintering is less consumed and practical.

Incidentally, the pre-sintered body in this embodiment was heated in a non-oxidizing atmosphere in the same manner as in the first embodiment.
When main sintering was performed at 00 ° C. for 10 minutes, no crack was generated in the obtained closed part structure 40, but the concave part 44 of the closed part structure 40 to which the closed tube 12 was connected, that is, a layer of only alumina Was not sufficiently sintered, the airtightness was reduced, and the high-pressure gas in the arc tube 11 leaked to some extent during lighting.

In Example 3, the amount of silica added was 5
Next, the presence or absence of high-pressure gas leakage during lighting was tested by changing the amount of silica shown in Table 3 in terms of vol%.
In this test, main sintering was performed at 1750 ° C. for 10 minutes. Table 4 shows the results.

[Table 4] As can be seen from this, when the added amount of silica is 5 vol% or more, no leakage occurs at the time of lighting, but when the added amount of silica is 0 vol% (that is, the same as the conventional example) and 2.5 vol%, it leaks. Therefore, when the main sintering temperature is 1750 ° C., the amount of silica added is 5 vol.
% Or more.

[0022]

As described above, the present invention relates to a non-closing portion structure of a bulb for sealing a closing tube formed of an alumina-based functionally gradient material and connected to an alumina arc tube. The end portion on the conductive region side is composed of a layer of only a non-conductive inorganic material component containing alumina as a main component, and at least a region in which the conductive inorganic material component is mixed with the non-conductive inorganic material component is made of alumina. Since the low-melting second non-conductive inorganic substance component is contained, high airtightness can be obtained even when the functionally graded material is fully sintered at a low temperature, and a tube which does not leak when the lamp is turned on can be obtained. An occlusion structure may be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a lamp using a closure structure according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Bulb 11 Arc tube 12 Occlusion tube 20 Electrode 30 Electrode core rod 40 Occlusion part structure 41 Non-conductive area side end face of occlusion part structure 42 Conductive area side end face of occlusion part structure 43 Central hole of occlusion part structure 44 Recess of closed part structure 50 Frit

Claims (2)

[Claims] 1. A substantially columnar shape in which a conductive inorganic material component and a non-conductive inorganic material component have a stepwise concentration gradient in a longitudinal direction, one of which is a non-conductive region and the other is a conductive region. In the closed part structure of the bulb, which is made of a functionally graded material and seals the closed tube connected to the alumina arc tube, the main component of the non-conductive inorganic substance component is alumina, The end on the region side is composed of a layer of only a non-conductive inorganic material component containing alumina as a main component, and at least in a region where a conductive inorganic material component is mixed with a non-conductive inorganic material component containing alumina as a main component. (3) A closed structure of a bulb, comprising a second non-conductive inorganic substance component having a lower melting point than alumina. 2. The structure according to claim 1, wherein the second non-conductive inorganic substance component is silica or glass containing silica as a main component.