| 摘要 |
<p>PURPOSE:To improve a luminus flux maintenance factor so as to reduce wear of a cathode tip by arranging a sintered material, consisting of high melting point metal powder, in a tube part of high melting point metal rich in ductility in a cathode, and specifying a point end angle and a relation represented by expression I. CONSTITUTION:In a cathode, a sintered material, consisting of high melting point metal powder and emitter powder, is arranged in a tube part of high melting point metal rich in ductility. The tip is formed in cone shape, and when assumed 20 deg. to 140 deg. for tip angle A, Dmm for diameter of the sintered material, W watts for lamp input and dmm for distance between electric wires, D/W is specified in the range represented by expression I. Here, when the tip angle A is smeller than 20 deg., cutting work is incapable, and when larger than 140 deg., a luminescent spot is made unstable. When D/W is decreased smaller than a specified value, the temperature of the sintered material rises high, and an emitter substance is evaporated to accelerate lighting deterioration.When D/W is increased larger than the specified value, the temperature of the sintered material is excessively decreased to generate an unstable discharge.</p> |
