JPS6035789B2 - Tube body for discharge lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel structure for sealing the end of a tube such as a cylindrical tube made of a material exhibiting anisotropic thermal expansion characteristics.

For example, arc tube materials for alkali metal vapor discharge lamps such as high sodium lamps are required to have heat resistance and alkali corrosion resistance.

For this reason, opaque, translucent polycrystalline aluminum oxide porcelain has been widely used as an arc tube material for this type of discharge lamp. However, this material is not necessarily satisfactory in terms of transmittance of emitted light and alkali corrosion resistance. For this reason, in recent years, aluminum oxide single crystals have been considered to have advantages such as superior translucency, excellent alkali corrosion resistance, and resistance to devitrification even at high inputs. Attempts have been made to use a certain transparent saphia as an arc tube material. When used as an arc tube for a discharge lamp, both ends of the arc tube must be sealed together with the current conducting portions of the electrodes.

For this reason, conventionally, sapphire arc tubes were sealed using metals such as niobium, titanium, and tantalum, which have similar coefficients of thermal expansion, or
A disc or cap-shaped device made of a material such as alumina porcelain is used. On the other hand, saphia is a heterogeneous material and exhibits different thermal expansion characteristics depending on its orientation.
The amount of thermal expansion in the C-axis direction is larger than in the direction perpendicular to the C-axis of the crystal. Therefore, when sealing the end of a Sahuaia arc tube with a tube end sealing component made of a material with consistent thermal expansion characteristics as described above, stress distortion may occur in the sealed portion, causing cracks. You can see it. Furthermore, with the conventional method of sealing at the end of the arc tube, stress and strain are likely to occur during sealing, and in addition, microcracks are likely to exist at the end of the tube, making it susceptible to mechanical breakage. There is. The purpose of the present invention is to eliminate the above-mentioned drawbacks in tube bodies such as cylindrical tubes made of materials such as saphia, which exhibit thermal expansion characteristics that vary depending on orientation, and to provide good sealing properties without causing stress distortion in the sealed portion of the tube body. It's about getting. For this purpose, a sealing part made of a material having the same thermal expansion characteristics as the pipe body is used, and at least one side of the pipe body is sealed with the sealing part at a position spaced inward in the length direction from the end of the pipe body. death,
Furthermore, the arrangement may be such that the amount of thermal expansion with respect to the orientation at this sealed location matches that of the tube. Hereinafter, the present invention will be explained in detail with reference to an example in which saphire is used as a material for a discharge lamp, particularly an arc tube and a tube end sealing part. FIG. 1 shows a discharge lamp in which a Safya disk 2 having a pair of electrodes 3 at positions spaced inwardly in the longitudinal direction from both ends of the Safire arc tube 1 is sealed with a ceramic sealant 4.

In Fig. 1, the tube axis direction of the Safya arc tube 1 and the crystal C-axis direction coincide, and correspondingly, the C-axis direction of the Safya disk 2 is also processed to match the arc tube axis direction. . Since the direction of the thermal expansion characteristic exhibited by Saphire is determined by the C-axis direction of the Saphire crystal, when arranged as described above, the directions of the thermal expansion characteristic exhibited by each of the Saphire arc tube 1 and the Saphire disk 2 match, and Since they are made of the same material, the amount of thermal expansion is also the same, so no stress strain remains due to sealing. Furthermore, since the sealing point is located away from the tube end, the mechanical strength of the sealing part can be increased. The crystal growth direction of sapphire does not necessarily coincide with the C-axis direction, and the best crystal growth is shown at an angle of about 60 degrees with the C-axis. It doesn't match the direction. FIG. 2 shows an embodiment in which the C-axis directions of the discharge lamp, particularly the sapphire arc tube 11 and the sapphire disk 12, do not coincide with the tube axis directions. In this case, the sealing point is located inward in the longitudinal direction from the end of the arc tube, as in the case of FIG. The arc tube 11 is sealed. In the figure,
The arrow 15 indicates the C-axis direction of the arc tube 11, and the arrow 16 indicates the C-axis direction of the Safya disk 12. The directions of the arrows 15 and 16 are made to coincide with each other. In this case as well, no stress strain is generated in the sealed portion between the Saphia arc tube 11 and the Saphia disk 12, and the mechanical strength can also be increased. As explained above, according to the alkali metal vapor discharge lamp using the present invention, even if a material with different thermal expansion characteristics depending on the orientation is used as the arc tube, the mechanical strength of the sealed part can be increased, and the stress strain can be increased. It is possible to manufacture a highly reliable discharge lamp by reducing the risk of breakage and by reducing the influence of microcracks that often exist at the ends of the tube.

In the discharge lamp using the present invention as described above, in order to prevent oxidation of the electrode lead portion, an appropriate protection tube may be provided near the end of the arc tube, and the high temperature portion of the lead wire may be filled with a non-oxidizing substance. Alternatively, by keeping it in a vacuum state, the modification disclosed in Japanese Patent Application No. 49-92356 "Discharge Lamp" (filed on August 14, 1989), such as producing a tubeless discharge lamp, can be carried out. You may do so. Of course, the above explanation has focused on discharge lamps, but the present invention is not limited thereto, and should be understood as a sealed structure of a tube body made of an anisotropic material that is used in a high temperature section.

Further, in the description of the present invention, an example is shown in which Safya is used as the tube material, but it goes without saying that the present invention can be applied to other materials as well.

Further, although the tube body material and the sealing part material are both made of Safya, the present invention can be applied to different materials as long as they have substantially similar thermal expansion characteristics.

[Brief explanation of the drawing]

FIGS. 1 and 2 are diagrams showing embodiments of the present invention. In the figure, 1 and 11 are arc tubes, 2 and 12 are parts for sealing the arc tube, 3 and 13 are electrodes, 4 and 14 are sealants, and arrows 15 and 16 indicate the C-axis direction of the material crystal. Multi-figure multi-figure 2

Claims (1)

[Claims] 1. A tube body for a discharge lamp, which is formed by sealing at least one end of a tube made of monocrystalline sapphire, which exhibits thermal expansion that varies depending on the direction, with a sealing component made of monocrystalline sapphire, which exhibits the same thermal expansion characteristics. , the sealing component is located entirely inside the tube in the longitudinal direction from the tube end of the tube, and is sealed against the inner wall surface of the tube at this position, and A tube body for a discharge lamp, characterized in that the amount of thermal expansion of the tube and the sealing component at the sealed portion is set to be equal in any direction.