JPH0467734B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a discharge lamp arc tube.

Conventional Structure and Problems Arc tube envelopes made of single crystal or polycrystalline alumina are used in arc tubes of discharge lamps such as high-pressure sodium lamps.

By the way, the softening point of single crystal or polycrystalline alumina is 2015℃, which is almost the same as the melting point.
It is well known that unlike quartz glass, it is not possible to heat it to its softening point and pinch it. For this reason, conventionally, one or more assembled structures having an arc tube envelope, a frit ring, and a conductor are arranged inside a cylindrical heating element.
A method is adopted in which the temperature of the heating element is raised by induction heating from the outside, the frit ring is melted, and the conductor is sealed to the end of the arc tube envelope. However, when there is only one assembled structure, this method poses no problem because the radiant heat from the heating element is almost uniform;
In the case of discharge lamps such as the following), multiple assembly structures are often arranged inside the heating element in order to reduce costs. The fritted ring portion is difficult to melt, and therefore the fritted ring melts unevenly, making it impossible to hermetically seal the conductor to the ends of a plurality of arc tube enclosures at the same time.

Therefore, in order to solve this problem, the inventor first developed a heating element in which a plurality of holes were formed so that the distance from the center of the heating element was equal and the mutual spacing in the circumferential direction was equal. An assembly structure having an arc tube envelope, a frit ring, and a conductor is placed in each hole, and the frit ring is melted by induction heating with a heating element from the outside, and the end of the arc tube envelope is heated. We proposed a method for manufacturing discharge lamp arc tubes in which a conductor is sealed in the inner part.

However, this method requires a relatively long heating time (approximately
However, if the heating time is shortened, the outer periphery of the heating element will heat up quickly, the center will heat up later, and the pores will heat up more quickly. Since the temperature of the portion between the heating element and the hole also rises with a delay, the temperature of the heating element tends to rise unevenly. For this reason, there was a problem in that it took a relatively long time until the temperature of the entire heating element became uniform.

Purpose of the Invention The present invention provides a method for simultaneously sealing a conductor at the end of a plurality of arc tube enclosures using a frit ring.
It is possible to uniformly melt multiple frit rings at the same time while shortening the heating time, and therefore the conductor can be hermetically sealed to the ends of these arc tube envelopes at the same time, increasing productivity. The present invention provides a method for manufacturing a good discharge lamp arc tube.

Composition of the Invention The present invention is a method for manufacturing a discharge lamp arc tube, in which a dielectric material having an electrode at the tip is sealed to the end of an arc tube envelope made of single crystal or polycrystalline alumina using a frit ring. A plurality of circular holes having the same diameter are formed in the heating element so that the distances from the center of the heating element are equal and the mutual intervals in the circumferential direction are the same, and the outer shape of the heating element is the same as that of each circular hole. has a shape formed by sequentially connecting parts of concentric circles formed on the outside of the heating element, and another hole is formed in the center of the heating element, and the arc tube enclosure, the frit ring, and the conductive The assembly structure having a body is placed in each of the plurality of holes one by one, and the frit ring is melted by induction heating the heating element from the outside, and the conductor is sealed at the end of the arc tube envelope. The present invention is characterized by a method of manufacturing a discharge lamp arc tube.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 are a plan view and a longitudinal cross-sectional view showing an example of a heating element used to carry out the method of manufacturing a discharge lamp arc tube of the present invention. heating element 1
A plurality of circular holes 2 having the same diameter are formed so that the distances from the center O are equal and the mutual intervals A in the circumferential direction are equal, and a separate hole 2 is formed in the center of the hole 2. A circular hole 3 is formed. That is, the angles θ formed by two adjacent straight lines connecting the center O of the heating element 1 and the center of the circular hole 2 are equal to each other. The outer shape of the heating element 1 is formed by sequentially connecting parts of concentric circles formed on the outside of each circular hole 2. Inside the circular hole 2, an arc tube envelope 4 made of single crystal alumina and a frit ring 5 are provided.
and an assembled structure having a tubular conductor 6 are placed one by one. An electrode 7 is provided at the tip of the conductor 6.

Such a device is installed in a container 8 which is in a vacuum or an inert gas atmosphere, and the heating element 1 is heated by induction heating from the outside by passing a current through the induction coil 9 to raise the temperature (see Fig. 3). The frit ring 5 is melted to seal the conductor 6 to the end of the arc tube envelope 4. In addition, in FIG. 3, 10 indicates support.

As described above, according to the present invention, a plurality of circular holes having the same diameter are arranged in the heating element 1 at the same distance from the center O and at the same mutual interval A in the circumferential direction. 2 is formed, and a circular hole 3 is also formed in the center thereof, and the outer shape of the heating element 1 is formed by connecting parts of concentric circles formed on the outside of each circular hole 2 in order. Therefore, the heat capacity of the central part of the heat generating element 1 decreases, and the heat capacity of a part of the outer periphery of the heat generating element 1 also decreases. For this reason, by arranging the assembly structure having the arc tube envelope 4, frit ring 5, and conductor 6 one by one in each of the circular holes 2, and heating the heating element 1 by induction from the outside, the heating element 1 can be heated in a short time. The temperature rises uniformly, and therefore the frit ring 5 also melts uniformly. As a result, the conductors 6 can be simultaneously and airtightly sealed to the ends of a plurality of arc tube enclosures 4 in a short time. FIG. 4 shows a conductor 6 at the end of the arc tube enclosure 4.
This shows the state in which they are hermetically sealed.

Next, a specific example of the present invention will be explained.

The heating element 1 is mainly made of carbon and has a diameter of 40 mm.
mm, height is 20mm. Six circular holes 2 with a diameter of 10 mm are provided in the circumferential direction of the heating element 1, and a circular hole 3 with a diameter of 11 mm is provided in the center thereof, and the distance from the center O to the center of the circular hole 2 is are each 13 mm, each angle θ is 60 degrees, and the mutual spacing A of the circular holes 2 in the circumferential direction is equal.

In the center of each circular hole 2 of such a heating element 1, an arc tube enclosure 4 made of polycrystalline alumina with an outer diameter of 6 mm, a frit ring 5 placed on one end surface of the arc tube enclosure 4,
A conductor 6 made of niobium is arranged to pass through a hole formed in the center of the frit ring 5. Fritz ring 5 is made of yttrium oxide (Y ₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ), calcium oxide (CaO) and magnesium oxide (MgO).
The melting point is approximately 1365℃. This device is placed in an atmosphere filled with 50 Torr of argon.
When the temperature of the heating element 1 was raised from room temperature to a maximum temperature of 1500°C in about 5 minutes by induction heating using an external 400kHz high-frequency power source, the fritted ring 5 melted almost uniformly and the multiple arc tube enclosures 4 The conductor 6 could be hermetically sealed at the same time to the end of the conductor 6. Thereafter, an arc tube for, for example, a high-pressure sodium lamp is obtained by a conventional method.

Note that the method of the present invention can be applied even when a substance such as sodium is enclosed in the arc tube container.

Further, the number of circular holes formed in the heating element increases or decreases depending on the size of the outer diameter of the arc tube enclosure.

Effects of the Invention As explained above, the present invention can melt the frit ring almost uniformly in a short period of time, and therefore can simultaneously and airtightly seal the conductor to the ends of a plurality of arc tube enclosures. Therefore, it is possible to provide a method for manufacturing a discharge lamp, which has good productivity and can significantly reduce costs.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an example of a heating element used for carrying out the method for manufacturing a discharge lamp arc tube of the present invention, FIG. 2 is a cross-sectional view taken along the line -- in FIG. FIG. 4 is a diagram illustrating an example of an apparatus for carrying out the method for manufacturing a lamp arc tube, and is a partial cross-sectional view showing a state in which a conductor is sealed to the end of the arc tube envelope. 1... Heating element, 2, 3... Circular hole, 4... Arc tube enclosure, 5... Fritt ring, 6... Electric conductor,
8... Container, 9... Induction coil.

Claims (1)

[Claims] 1. A method for manufacturing a discharge lamp arc tube, in which a conductor having an electrode at the tip is sealed to the end of an arc tube envelope made of single crystal or polycrystalline alumina using a frit ring, and the center of the arc tube is sealed to the heating element. A plurality of circular holes having the same diameter are formed so as to be located at equal distances from the heating element and at equal intervals from each other in the circumferential direction, and further, the outer shape of the heating element is formed on the outside of each circular hole. an assembly structure having a shape formed by sequentially connecting parts of concentric circles, and having another hole formed in the center of the heating element, and comprising the arc tube enclosure, the frit ring, and the conductor. are arranged in each of the plurality of holes, and the frit ring is melted by induction heating of the heating element from the outside, and the conductor is sealed to the end of the arc tube envelope. A method for manufacturing a discharge lamp arc tube.