JPH04101348A - High voltage discharge lamp - Google Patents

Abstract

PURPOSE:To eliminate discharge caused between an electrode and a metal foil and prevent cracking formation by winding a metal foil on the outer circumference of a base end part of an electrode and avoiding void formation in the surrounding of the metal foil. CONSTITUTION:A metal foil 4 made of molybdenum is wound on the outer circumference of the base end part 3 of an electrode made of tungsten and extending from a sealed tube part 2 of a bulb 1 made of quartz glass. The thickness of the metal foil 4 needs to be within 10-17mum. Consequently, a glass tube 5 for holding and the bulb 1 made of glass and put in the outside of the tube 5 are squeezed under heating condition and thus voids are not formed in the circumference of the metal foil 4. As a result, discharge does not possibly occur between electrodes 9, 10 and the metal foil 4 at the early stage of the lighting of a high voltage discharge lamp and crack formation due to the difference of thermal expansions of the electrode base end part 3 and the glass tube 5 for holding is prevented effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-pressure discharge lamp having a structure in which the base end of an electrode is held by a holding glass tube via a metal foil.

[Conventional technology]

In high-pressure discharge lamps, when the IrL pole becomes large, an electrode with a structure in which the base end is thinner than the tip end is usually used, so the glass bulb part required to hold the end of the electrode 7J is The larger the amount of reduction, the more difficult it is to process.

For this reason, in conventional high-pressure discharge lamps, a glass tube is placed so as to cover the base end of the electrode, and the glass tube and its outer surface are exposed under heating. It has been proposed to reduce the amount of narrowing of the glass bulb part by welding the glass bulb part.

Furthermore, in order to prevent the occurrence of cracks due to the difference in thermal expansion between the glass bulb and the electrode, a method has been proposed in which a metal foil is wound around the outer periphery of the base end of the electrode.

For example, Japanese Unexamined Patent Publication No. 143358/1983 proposes a high pressure discharge lamp in which the base end of an electrode is brought into elastic contact with a glass bulb via a metal foil provided with unevenness.

For example, Japanese Patent Application Laid-Open No. 1-151149 proposes a high-pressure discharge lamp that is sealed to a glass bulb via a metal foil that is loosely wound so as to leave a gap around the base end of the electrode. has been done.

[Invention or problem to be solved]

In the above-mentioned conventional technology, in order to efficiently absorb the thermal expansion of the electrode base end and prevent the glass bulb from cracking, a thick metal foil or the like is placed between the electrode base end and the glass bulb. A large void was intentionally created by interposing the uneven metal foil.

However, if there is a large gap around the metal foil, the temperature of the metal foil tends to rise in the early stages of lighting, and discharge is likely to occur between the metal foil and the electrode. There is a problem with the glass in the stop tube deteriorating due to heat.

On the other hand, if the metal foil is made too thin, it tends to break easily, resulting in poor workability.

An object of the present invention is to prevent the occurrence of cracks caused by thermal expansion of the electrode base end by interposing a metal foil around the outer periphery of the electrode base end, and to suppress electrical discharge between the electrode and the metal foil. An object of the present invention is to provide a high-pressure discharge lamp that prevents thermal deterioration of metal foil and sealed tube parts.

[Failure to solve the problem]

In order to achieve the above object, the high pressure discharge lamp of the present invention has a metal foil having a thickness of 10 to 178 m wrapped around the outer periphery of the base end of the electrode extending from the sealed tube part of the glass bulb. A holding glass tube is arranged so that the holding glass tube and the metal foil are located inside the tube, and the holding glass tube and the glass bulb portion located outside of the holding glass tube are squeezed together under heat and welded together. It is characterized in that the base end of the electrode is held by the holding glass tube via a metal foil so that no gap is formed between the electrode and the inner wall of the glass tube.

[Effect]

The thickness of the metal foil wound around the outer periphery of the electrode base end is 10 to 17 mm.
The holding glass tube and the glass bulb part located outside thereof are squeezed under heating within the range of μm,
Since no voids are formed around the metal foil, there is no risk of discharge occurring between the electrode and the metal foil during the initial lighting of the sitting pressure discharge lamp. Moreover, the presence of the metal foil prevents direct welding between the holding glass tube and the electrode base end, which effectively prevents the occurrence of cracks caused by the difference in thermal expansion between the electrode base end and the holding glass tube. Prevented.

〔Example〕

The present invention will be explained in detail below.

For example, in an ultra-high pressure discharge lamp with an output of 1 kW, as shown in FIG. A metal foil 4 made of molybdenum and having a thickness of 13 μm is wound around the outer periphery of about 1.5 turns.

A holding glass tube 5 made of quartz glass and having an inner diameter of approximately 3.5 mm is arranged so that the electrode base end 3 and metal foil 4 are located inside the tube, and a holding glass tube 5 and a holding glass tube 5 with an inner diameter of about 3.5 mm are arranged so that the electrode base end 3 and metal foil 4 are located inside the tube. While heating the glass bulb part 6, the inside of the glass bulb 1 is heated to IX10-' to IX
By reducing the pressure to about 10-' Torr, the glass bulb part 6 and the holding glass tube 5 are squeezed, and as shown in an enlarged view in FIG. are welded to each other, and the electrode base end 3 is held by the holding glass tube 5 via the metal foil 4 so that no gap is formed between the holding glass tube 5 and the inner wall of the holding glass tube 5. In FIG. 1, 7 is a bulge, 8 is a discharge space, 9 is an anode, ] 0 is a cathode, 11 is a metal foil for sealing,
12 is a cap.

The thickness of the metal foil 4 must be in the range of 10 to 17 μm. When the thickness of the metal foil 4 is less than 10 μm, the molybdenum metal foil is easily damaged, resulting in poor workability. On the other hand, when the thickness of the metal foil 4 exceeds 17 μm, the springback force of the molybdenum metal foil is strong.
An unnecessarily large gap is created around the metal foil, making it easy for discharge to occur between the electrode and the metal foil.

Table 1 shows experimental data when the thickness of the metal foil 4 was actually varied.

Table 1 Also, the number of turns of the metal foil 4 is preferably about 1.0 to 2.0 turns. If the number of windings is less than 1.0 tan, there will be a portion where the electrode base end 3 and the holding glass tube 5 are directly welded, and cracks are likely to occur due to the difference in thermal expansion between the two. On the other hand, when the number of windings exceeds 2.0 turns, more voids are formed around the metal foil than necessary, making it easy for discharge to occur between the electrode and the metal foil.

In addition, in order to reliably prevent welding between the holding glass tube 5 and the electrode base end 3, one end and the other end of the metal foil 4 are slightly protruded from both ends of the holding glass tube 5, respectively. There is.

According to the above embodiment, the thickness of the metal foil 4 wound around the outer periphery of the electrode base end 3 is defined to be in the range of 10 to 17 μm, and the holding glass tube 5 and the glass bulb located outside thereof are Since the portion 6 is compressed under heating to prevent a gap from forming around the metal foil 4, there is no risk of discharge occurring between the electrode and the metal foil 4 during the initial lighting of the high-pressure discharge lamp, and the metal foil 4 is heated. The presence of the foil 4 prevents direct welding between the holding glass tube 5 and the electrode base end 3, which effectively prevents the occurrence of cracks caused by the difference in thermal expansion between the electrode base end 3 and the holding glass tube 5. Prevented.

〔Effect of the invention〕

As explained above, according to the high-pressure discharge lamp of the present invention, the metal foil is wound around the outer periphery of the electrode base end and no gap is created around the metal foil, so that the electrode and the metal foil are There is no risk of electrical discharge occurring between the electrodes, and there is no risk of cracks occurring due to the difference in thermal expansion between the electrode base end and the holding glass tube. Therefore, it is possible to prevent thermal deterioration and cracking of the metal foil and holding glass tube.
It is possible to obtain a high pressure discharge lamp with a long service life.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a high-pressure discharge lamp according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional side view showing the state of the metal foil.

Claims (1)

[Claims] Metal foil with a thickness of 10 to 17 μm is wound around the outer periphery of the electrode base end extending from the sealed tube of the glass bulb, and a holding glass is wrapped so that the electrode base end and the metal foil are located within the tube. The tube is placed, and the holding glass tube and the glass bulb portion located outside the holding glass tube are heated and squeezed so that they are welded to each other and there is no gap between the holding glass tube and the inner wall of the holding glass tube. A high pressure discharge lamp characterized in that an electrode base end is held by the holding glass tube through a metal foil.