JPH0429482Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention is a high-pressure metal vapor discharge lamp (hereinafter referred to as HID).
(referred to as a lamp)
More specifically, the present invention relates to a conductive closing body for closing both ends of a translucent ceramic tube constituting an arc tube.

Traditionally, translucent ceramic tubes have been used.
As an end blocker for the arc tube in HID lamps,
Conductive disks have been proposed in Japanese Patent Laid-Open Publication No. 71695/1983. Such a conductive disk is made of, for example, a conductive cermet made by mixing aluminum oxide powder and metallic tungsten powder and sintering it, and the part of the conductive cermet located inside the arc tube has a A tungsten electrode is provided, and a lead member is embedded and fixed in the outer surface of the conductive cermet, so that power is supplied from the lead member to the tungsten electrode through the outer conductive cermet. . The reason for using a conductive cermet disk with such a structure is that, when applied to a high-pressure sodium lamp, for example, it avoids the use of expensive niobium metal, and it also avoids the use of the inside of an arc tube made of translucent ceramics. In addition, when applied to a so-called metal halide lamp in which a suitable type of luminescent metal halide is sealed together with mercury and a rare gas, it has halogen resistance.

However, in the case of HID lamps equipped with arc tubes closed with such cermet disks, when the lamp is started, the arc does not come out from the electrode tip but is generated from the conductive cermet part, due to the so-called back arc phenomenon. In addition, cracks occur in such disks, resulting in leakage of the arc tube, and heat-resistant metal components of the cermet material that evaporate and scatter from the disk adhere to the inner wall of the arc tube, turning it black, leading to a decrease in luminous flux, etc. There was a problem.

The present invention has been developed in view of the above circumstances, and its purpose is to provide an arc tube end closure for an HID lamp that does not cause back arcing during startup. In order to achieve this objective, in a closure body consisting of a conductive disk that supports a predetermined electrode and closes the end of the arc tube, the electrode side surface of the conductive disk exposed inside the arc tube is coated with such a surface. An electrically insulating layer having a coefficient of thermal expansion similar to that of the conductive disk material was integrally provided so as to cover the entire surface without using any adhesive layer.

Hereinafter, in order to clarify the present invention more specifically, one embodiment of the present invention will be described in detail based on the drawings.

First, FIG. 1 schematically shows the entirety of an HID lamp to which the present invention is applied, in which 2 is a bag-shaped or bulb-shaped bag-like or bulb-shaped light-transmitting material generally made of glass or the like. The opening of the outer tube 2 is closed with a cap 4, so that the inside of the outer tube 2 is sealed. Note that an inert gas such as nitrogen is sealed inside the outer tube 2, or it is maintained in a vacuum state. As is well known, conductive members 10, 10 supporting the arc tube 6 are connected to lead members 8, 8 at both ends of the arc tube 6 housed inside the outer tube 2 through the base 4. Power is supplied via the

Further, the luminous tube 6 is made of a tube-shaped translucent ceramic tube 12 made of alumina porcelain or the like.
and conductive disks 14, 14 as end caps fixed to both ends thereof to seal them.
It is composed of. In addition, inside the sealed translucent ceramic tube 12 of this arc tube 6,
Depending on the type of HID lamp, various metals or their vapors are filled in. For example, high-pressure sodium lamps are filled with metallic sodium, mercury, and rare gases, and metal halide lamps are filled with mercury and their vapors. Along with the rare gas, an appropriate type of luminescent metal halide (thallium iodide, sodium iodide, indium iodide, etc.) is sealed.

By the way, the present invention is applied to such a conductive disk member 14 as an end cap, in other words, to a conductive closing member at the end of an arc tube, an example of which is shown in FIG. There is. That is, in FIG. 2, the conductive disk 14 is fitted and fixed to the end of the translucent ceramic tube 12 of the arc tube 6 with a sealing material 19 such as glass frit, and a lead member is attached to the outer surface of the conductive disk 14. A well-known electrode 16 such as a tungsten electrode is provided on the inner surface of the ceramic tube 8, in other words, on the surface exposed inside the translucent ceramic tube 12.
is erected with a part of it buried, and is located at the center of the translucent ceramic tube 12. And this conductive disk 1
An electrical insulating layer 20 is provided on the discharge surface 18 on the electrode 16 side of No. 4.
is provided directly, that is, integrally with a predetermined thickness without using any adhesive layer, and such discharge surface 18
It covers the entire surface.

Therefore, in the case of the arc tube 6 in which such an insulating layer 20 is provided on the discharge surface 18 of the conductive disk 14, power is supplied to the lead member 8 at the time of startup through the insulating layer 20, and a predetermined voltage is applied. Even if the voltage is applied between the electrodes 16, 16 at both ends, the discharge surface 18
This effectively suppresses the back arc phenomenon that causes discharge from the electrode 16, and the arc is effectively generated from the tip of the electrode 16. Therefore, the occurrence of cracks in the disk 14, which were conventionally caused by the back arc phenomenon, as well as the occurrence of leaks due to this, can be effectively prevented, and the heat-resistant metal component of the cermet material evaporates from the disk 14. This eliminates the problem of blackening of the inner surface of the arc tube 6, specifically the translucent ceramic tube 12, due to the adhesion of such heat-resistant metal components. This makes it possible to eliminate all problems such as a decrease in luminous flux.

In this way, various known materials are appropriately selected as the material for the conductive disk 14 used as the end closure of the arc tube 6, but in general, the translucent ceramic tube 12 is used. Any conductive material can be used as long as it has an intermediate coefficient of thermal expansion between the constituent materials and the heat-resistant metal used as the electrode 16 and the lead member 8. For example, tungsten metal or molybdenum metal and aluminum oxide can be used. Composites such as tungsten carbide, tungsten boride, etc. are used.

Further, the insulating layer 20 provided on the surface 18 of the conductive disk 14 on the electrode 16 side is appropriately formed using a known electrically insulating material. It is necessary to form the insulating layer 20 using a heat-resistant and insulating-resistant ceramic having a coefficient of thermal expansion close to that of . Such an insulating layer 20 can be formed by various known methods. For example, the insulating layer 20 can be formed by integrally molding and sintering the conductive disk material and the above-mentioned insulating material, or by forming it in advance by molding and sintering the conductive disk material and the insulating material. There is no problem in forming the coating by coating the surface of the sintered conductive disk 14 by a method such as frit sealing, thermal spraying, or vapor deposition. In this way, the electrically insulating layer 20 having a coefficient of thermal expansion similar to the material of the electrically conductive disc 14 is applied to the electrically conductive disc 14.
4, the occurrence of cracks or cracks due to differences in thermal expansion can be advantageously prevented by forming the film integrally over the entire surface of the film without intervening an adhesive layer or the like. It was summer. Furthermore, the integral formation of the electrically insulating layer 20 facilitates handling when sealing the electrically conductive disk 14 to the arc tube 6.
Since there is no gap at the bonding surface between the conductive disk 14 and the conductive disk 14, there is no contact with the electrode mandrel due to adhesive inflow, and there is an advantage that no cracks in the adhesive layer occur. Note that when the electrically insulating layer 20 is provided on the conductive disk 14 via a mounting layer, due to the difference in thermal expansion coefficient between the adhesive layer and the electrically insulating layer 20, and furthermore, the conductive disk 14. ,
Problems such as cracks and cracks are likely to occur in the electrical insulating layer 20, adhesive layer, etc. due to rapid heating applied during lighting and the like.

Such an insulating layer 20 must be applied at least to the electrode-side surface (discharge surface 18) of the conductive disk 14, which is a closure body.
Further, the present invention is not limited to this, and there is no problem even if the arrangement is provided over the entire surface of the disk 14. The thickness of the coating layer 20 will be appropriately determined within a range that can effectively suppress the back arc phenomenon, which is the purpose of the present invention, but it is generally formed to a thickness of about 0.05 to 0.8 mm. It will be done.

Note that, as described above, an HID lamp in which the closure body 14 on which the insulating layer 20 according to the present invention is formed is made of a translucent ceramic tube 1.
For example, a metal halide lamp or a high-pressure sodium lamp using 2 as a constituent material of the arc tube 6 can be mentioned.

Although a typical example of the present invention shown in the drawings has been described above, the present invention is not to be construed as being limited by the illustrated structure or the specific explanation accompanying it. Without departing from the spirit of the present invention, various changes, modifications, improvements, etc. may be made to the present invention based on the knowledge of those skilled in the art, and the present invention does not include such embodiments. It goes without saying that this also includes the following.

As is clear from the above explanation, the HID lamp equipped with an arc tube formed by closing both ends of a translucent ceramic tube with a closing body according to the present invention does not generate back arc when starting. The disk constituting the closing body is not damaged, and therefore the reliability of the lamp is improved, and there is no blackening, resulting in a high luminous flux maintenance rate. Since an electrically insulating layer with a coefficient of thermal expansion similar to that of the disk material is integrally formed on the surface of the disk without any intermediary, handling of the conductive disk when it is enclosed in the arc tube becomes easier. In addition, the problem of cracks in insulating layers caused by differences in thermal expansion can be successfully solved, and this is where the great industrial significance of the present invention lies. .

[Brief explanation of the drawing]

FIG. 1 is a schematic cutaway diagram showing an example of an HID lamp equipped with an arc tube in which both ends of a translucent ceramic tube are closed with a closure body according to the present invention, and FIG. FIG. 2 is an explanatory cross-sectional view of a main part showing an enlarged end portion of FIG. 2... Outer tube, 4... Cap, 6... Luminescent tube, 8...
... Lead member, 10 ... Conductive member, 12 ... Transparent ceramic tube, 14 ... Conductive disk,
16... Electrode, 18... Discharge surface, 19... Sealing material, 20... Insulating layer.

Claims (1)

[Scope of utility model registration request] In a closing body consisting of a conductive disk that supports a predetermined electrode and closes the end of the arc tube, the surface of the conductive disk on the electrode side exposed inside the arc tube is covered with a material such that the entire surface is covered. A conductive end of an arc tube for a high-pressure metal vapor discharge lamp, characterized in that an electrical insulating layer having a coefficient of thermal expansion similar to that of a conductive disk material is integrally provided without any adhesive layer. Obstruction body.