JPH0555972B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a high-pressure discharge lamp in which the electrode sealing portion of an airtight container such as a quartz arc tube is improved.

[Technical background of the invention and its problems]

In general, high-pressure discharge lamps use thick and large electrodes made of high-melting-point metals such as tungsten. The end of an airtight container made of glass is sealed with a metal foil made of a high melting point metal such as molybdenum interposed therebetween. The anode side of DC-lit lamps and large-capacity AC-lit lamps are equipped with electrodes that are enlarged to match the current consumption, but the sealing metal foil connected to these electrodes is Although the width is increased, the thickness is extremely thin, with a maximum value of about 20 to 35 μm, in order to improve the sealing properties with the quartz glass.

In the case of such lamps, especially when they are used frequently with flashing, the repeated expansion and contraction of the electrodes causes the metal foil connected to the electrodes to expand and contract as well, resulting in an extremely thin foil-like structure. The metal foil sometimes broke during use, causing the lights to not turn on. In particular, the anode side of a DC-lit lamp consumes more power at the electrode than its cathode side or an AC-lit lamp, so the incidence of the above-mentioned accidents was high.

In addition, in the case of a large electrode such as the anode in the above-mentioned DC-lit lamp, the wall thickness should be thinner on the distal end side of the proximal end that is sealed to the sealing part of the airtight container. Formed flat. This is because reducing the thickness of the sealed portion of a large electrode improves the strength of the sealed portion and increases its reliability. However, when a flat part is formed in this way, stress concentrates on the edge part of the flat part,
Particularly in high-pressure discharge lamps where the internal pressure of the airtight container is 10 atmospheres or more when lit, there is a risk that cracks may occur in the glass seal.

[Purpose of the invention]

This was made to address the above-mentioned drawbacks of the present invention,
In addition to preventing defects due to cutting of the sealing metal foil, the internal pressure when lit is 10%, which improves the strength of the sealing part.
The purpose of the present invention is to provide a high-pressure discharge lamp that has a pressure higher than atmospheric pressure.

[Summary of the invention]

In the present invention, a pair of electrodes is provided oppositely by sealing the proximal end portions to both end sealing portions of a quartz glass airtight container.
In a high-pressure discharge lamp in which the above-mentioned electrode is connected to the external introduction body through a metal foil for sealing, and the internal pressure is 10 atmospheres or more when lit, at least one of the electrodes has a thin wall at its large-diameter base end. The thin walled portion is sloped so that the tip side is thicker, and the thickness at the tip of the thin walled portion is t (mm), and the diameter of the large diameter base end is D (mm). ), the high pressure discharge lamp is characterized in that 0.35≦t/D≦0.55.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

Figure 1 shows a 500W class xenon lamp.
is an airtight container made of quartz glass filled with xenon gas in an amount of about 40 atmospheres when lit, and consists of an elliptical spherical main body 2 surrounding a discharge space and sealing parts 3A and 3B extending at both ends of the main body 2. 4 is a cathode with a diameter of about 3 mm, its base end 4a is sealed to a sealing part 3B, and two sealing metal foils 6B, 6B made of molybdenum, for example, are sandwiched between a quartz body 5 called a separator glass. It is connected to the external introduction body 7B via the external introduction body 7B. 8 is an anode, and its base end 8a has a diameter D of 6 mm.
is sealed to the other sealing part 3A, and as shown in an enlarged view in FIG. When viewed from the thickness direction, a slope is formed such that the wall thickness at a is 2.2 mm and the wall thickness t on the tip end 9a side is 2.7 mm, forming a wedge shape. 6A and 6A are each 5mm wide and 26μ at the maximum pressure.
A quartz body 5 called a separator glass is clamped in the same way as on the cathode 4 side with a metal foil for sealing made of molybdenum, which is extremely thin as m, and one end is connected to the anode 8 via platinum (not shown), and the other end is connected to the anode 8 via platinum (not shown). The sides are each connected to the external introduction body 7A. (In addition,
The drawings are slightly exaggerated for convenience of explanation. ) In the xenon lamp having such a configuration, a slight gap is created between the quartz glass of the sealing part 3A and the quartz glass of the sealing part 3A, similar to the conventional lamp, in the vicinity of the contact area between the quartz body 5, which is the separator glass, and the anode 8. Even if the anode 8 expands or contracts when the lamp flashes, the shape in the thickness direction of the thin section 9 on the base end side of the anode is such that the tip section 9a side is thick. Since the thin wall portion 9 is wedge-shaped, the thin wall portion 9 is wedge-bonded to the quartz glass of the sealing portion 3A, and expansion and contraction are moderated, so that the expansion and contraction force applied to the metal foils 6A and 6A is also weak. Therefore, foil breakage due to mechanical fatigue can be prevented.

Next, we will discuss the conventional lamp, that is, the one in which the thickness of the thin wall portion 9 formed at the base end of the anode is constant, referring to FIG. For each piece, (5 minutes on - 5 minutes off)
As a result of repeated comparisons of flashing tests, it was found that all of the lamps of this example had no abnormalities even after 3000 flashing cycles, while the conventional lamp had 1 flashing after 1200 flashings, 1 flashing after 1500 flashings, and 1 flashing after 2200 flashings. By the 3,000th cycle, there was one defective foil cut and three by the 3000th cycle, and although the remaining two foils did not completely break, there were some abnormalities that showed signs of foil breakage.

Incidentally, referring to FIG. 2, the wedge-shaped inclination of the anode thin section 9 is defined as ta/2l (in the above embodiment, ta/2l≒1.8/50), but this value is 1/2l. It is preferable to set it in the range of 5 to 1/50; if it is larger than 1/5, the above-mentioned slope becomes too steep and stress concentration becomes large, causing negative effects such as a decrease in pressure resistance. If it is smaller than /50, the foil breakage prevention effect will be weakened, and the above effect will also be affected by manufacturing variations, especially variations in the gap 10 that occurs between the thin wall portion 9 of the anode base end and the quartz glass of the sealing portion 3A. As a result, there may be some signs of foil breakage due to repeated blinking of the lamp.

Furthermore, the thickness t of the tip 9a of the thin portion of the anode 8
(2.7 mm) and the diameter D (6 mm) of the large-diameter proximal end 8a is formed so that the ratio t/D is 0.45, so even if the internal pressure of the airtight container at the time of lighting is as high as about 40 atm. However, no cracks occurred in the sealing portion 3A.

As a result of various experiments, it has been found that the above relationship of t/D is preferably within the range of 0.35≦t/D≦0.55. That is, if t is too small (t/D<0.35), not only the support strength of the anode 8 having a large tip and heavy weight will be reduced, but also the pressure strength of the sealing portion 3A will be reduced. In other words, Figure 3 is
This is a cross-sectional view of the sealing part 3A taken along line A-A' in the figure, and when the pressure inside the airtight container 1 is high, the four corners 10a of the tip 9a of the anode thin wall part 9,
Stress is concentrated on 10b, 10c, and 10d, but if the wall thickness t of the tip 9a is too small, the corners 10a and 10c, and also the corners 10b and 10d, become close to each other, and the stress concentration at these close portions is It becomes even stronger, and glass cracks in the sealing portion 3A are more likely to occur.

On the other hand, if t is too large (t/D>0.55), the problem of the corners of the thin anode tip 9a being too close together as in the case where t is too small does not occur, but the corners 10a and 10c and the corners 10b and 10d Since the length of the line segment connecting the lines, that is, the length of the line segment on which stress is concentrated, increases, this is not preferable in terms of measures against glass cracks in the sealing part.
Since the wall thickness of the quartz glass of the sealing portion closest to the four points d also decreases, the pressure resistance strength also decreases, which is not preferable.

Furthermore, unlike the case of the above embodiment, in a lamp that uses only a metal foil for sealing directly without intervening a quartz body 5 such as a separator glass, if t is too large, the thickness of the extremely thin metal foil will increase. This increases the degree of deformation of the metal foil during the sealing process, creating a risk of foil breakage.

In addition, in the case of a DC-lit lamp as in the above example, it is particularly effective on the anode side, where the temperature becomes high, but even on the cathode side, the foil due to the expansion and contraction of the cathode as the current increases. Since breakage cannot be ignored, it is preferable to use the same structure as the anode side.Also, even in large capacity AC lighting type lamps, each electrode acts as an anode every half cycle, causing a considerable amount of damage. Since the temperature is high, it is preferable that both electrodes have the same structure as the anode side in the above embodiment.

Furthermore, the present invention has similar effects on xenon lamps that do not use separator glass, and is not limited to xenon lamps, but can also be applied to other high-pressure discharge lamps such as high-pressure mercury lamps and ultra-high-pressure mercury lamps. be.

〔Effect of the invention〕

As detailed above, according to the present invention, the electrode, particularly the cutting caused by the expansion and contraction of the sealing metal foil connected to the electrode side which becomes high temperature, occurs when the high pressure discharge lamp blinks.
Not only can malfunctions be prevented, but even if the internal pressure during lighting is 10 atmospheres or more, breakage of the sealing part can be prevented, and a highly reliable and long-life lamp can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a xenon lamp which is an embodiment of the present invention, FIG. 2 is a longitudinal sectional view of the anode side sealing part which is the main part, and FIG. FIG. 3 is a cross-sectional view of the anode-side sealing portion taken along line A'. 1... Airtight container, 3A, 3B... Sealing part, 6A
...Metal foil for sealing, 4...Cathode, 8...Base end of anode, 9...Thin wall part, 9a...Tip of thin wall part,
t...Thickness at the tip of the thin anode part, D...Thickness at the base end of the large diameter anode.

Claims (1)

[Scope of Claims] 1. A pair of electrodes are provided oppositely by sealing the proximal end portions to both end sealing portions of an airtight container made of quartz glass, and the electrodes are connected to an external introducing member via a metal foil for sealing. In a high-pressure discharge lamp which has an internal pressure of 10 atmospheres or more when lit, at least one electrode has a thin part formed at its large-diameter base end, and the thin part is thicker on the tip side. Form a slope so that it becomes thick, and when the thickness of the tip of the thin section is t (mm) and the diameter of the large diameter base end is D (mm), 0.35≦t/D≦0.55. A high-pressure discharge lamp characterized by: