| 摘要 |
PROBLEM TO BE SOLVED: To provide an arc tube capable of improving reliability at a sealing part of a small diametrical cylinder part. SOLUTION: Lead wires 27a, 27b are inserted into small diametrical cylinder parts 23a, 23b of a translucent ceramic made valve 20. The lead wires 27a, 27b are arranged on head ends of electrides 24a, 24b projected in an electric discharge space 22 of a spherical part 21. Metal pipes 28a, 28b are provided between the lead wires 27a, 27b and the small diametrical cylinder parts 23a, 23b along the peripheral direction on a part of the lead wires 27a, 27b. Airtightness with the outside is held by fixing the metal pipes 28a, 28b, the lead wires 27a, 27b and the small diametrical cylinder parts 23a, 23b by sealing members 29a, 29b. A space with the lead wires 27a, 27b on the inside of the small diametrical cylinder parts 23a, 23b is reduced by the metal pipes 28a, 28b. Quantity of the sealing members 29a, 29b to flow in between the small diametrical cylinder parts 23a, 23b and the lead wires 27a, 27b is decreased. It is possible to improve reliability at the sealing parts of the small diametrical cylinder parts 23a, 23b at the time of lighting the arc tube 12 at the time of sealing and fixing the lead wires 27a, 27b on the small diametrical cylinder parts 23a, 23b.
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