JPH1040867A - Discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp capable of preventing itself from breakage during lighting by completely welding a blocked body, formed with an inclination function material to a block tube. SOLUTION: A lamp has a pair of electrodes 20, 30 arranged opposite to each other in an arc tube 11 for a non-conductive discharge container and discharge gas filled therein. Cylindrical block tubes 12 formed at the end of the arc tube 11 are blocked by a blocked bodies 50 formed with an inclination function material molded of non-conductive powder, such as silica and conductive powder such as molybdenum. In this case, approximately conical or semispherical openings 54 are formed in the end face 51 of the blocked body 50 fitted into the block tube 12 toward the arc tube 11 and the opening edge of the opening 54 is formed thin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp in which an end of a discharge vessel is closed with a functionally gradient material.

[0002]

2. Description of the Related Art In a discharge lamp, a pair of electrodes are arranged opposite to each other in a spherical or elliptical arc tube of a quartz glass discharge vessel, and a luminous metal such as mercury and a discharge gas are sealed therein. A tubular blocking tube is connected to the end of the arc tube, and the electrode bar and the external lead bar are closed while being electrically connected by the blocking tube. Since the closed tubes made of aluminum have significantly different coefficients of thermal expansion, they cannot be closed by directly welding the closed tubes to the electrode rods. For this reason, conventionally, the closed pipe has been closed by a step connection method, a foil sealing method, or the like.

[0003] In the step joining method, several kinds of intermediate glass tubes whose coefficient of thermal expansion sequentially approaches the coefficient of thermal expansion of tungsten from the coefficient of thermal expansion of quartz glass are prepared, and these intermediate glass tubes are connected to the end of the closed tube of the discharge vessel. The glass tube at the end closest to the coefficient of thermal expansion of tungsten is welded to the electrode rod. If the number of intermediate glass tubes is reduced, the difference in the coefficient of thermal expansion between adjacent intermediate glass tubes will increase, and the mechanical strength of the joint will be weak, and it will also be weak against thermal shock, reducing reliability. It is necessary to increase the number of tubes. Further, since the tungsten rod and the end of the glass are in contact with the air, if the temperature becomes higher than 400 ° C. during lighting, the tungsten is oxidized, and there is a risk of leakage or breakage. Therefore, the length of the occlusion tube in the axial direction is increased, and the number of joints is increased.

In the foil sealing method, the ends of an electrode rod and an external lead rod are welded to both ends of a molybdenum foil having a thickness of several tens of μm, and the molybdenum foil is sandwiched between quartz glasses to form a center of the molybdenum foil. A quartz glass closing tube is welded to the portion. In this foil sealing method, since the end of the molybdenum foil to which the external lead rod is welded is in contact with air, the molybdenum foil is oxidized when the temperature rises to 350 ° C. or more during lighting,
The seal portion may peel off due to expansion due to oxidation, leak or break. That is, since it is necessary to suppress a rise in temperature of the seal portion at the end of the closed tube, it is necessary to lengthen the closed tube to increase the distance between the arc tube and the seal portion, which becomes hot during lighting.

In the case of a discharge lamp using mercury vapor, if the distance between the arc tube and the sealing portion is increased, the temperature of the tube wall at the base of the electrode rod becomes low, that is, the coldest point temperature becomes too low. Mercury does not evaporate sufficiently. For this reason, it is necessary to form a heat insulating film on the outside of the tube wall at the base of the electrode rod to keep the temperature. However, there is a problem that light is blocked by the heat insulating film and light use efficiency is reduced.

As described above, according to the step joining method or the foil sealing method, the closed tube of the discharge lamp is elongated in the axial direction, but one closed tube of the short arc type discharge lamp is placed at the central opening of the concave reflecting mirror. In the light irradiation device in which the other closed tube extends in the optical axis direction of the concave reflecting mirror, a part of the reflected light of the concave reflecting mirror is long because the closing tube extends in the optical axis direction of the concave reflecting mirror. However, there is a problem that the light use efficiency is reduced because the light is incident on the closed portion and is blocked.

Recently, attention has been paid to a discharge lamp in which a closed tube at the end of a discharge vessel is closed with a closed body made of a functionally graded material formed of a non-conductive powder such as silica and a conductive powder such as molybdenum. Have been. The closed body formed of such a functionally gradient material has one end rich in a non-conductive component such as silica, and the proportion of a conductive component such as molybdenum is continuously increased toward the other end, or It increases gradually. Therefore, in the case of a functionally graded material formed of silica powder and molybdenum powder, the vicinity of one end of the closing body is non-conductive and has a coefficient of thermal expansion close to the coefficient of thermal expansion of quartz glass, and the other end. The neighborhood is
It is electrically conductive and has a coefficient of thermal expansion close to that of molybdenum.

[0008] Such a functionally graded material can increase the gradient at which the ratio between the non-conductive component and the conductive component changes, so that the closure formed of the functionally graded material has a short axial length. Also, the non-conductive component on one end face can be made rich and the conductive component on the other end face can be made rich. In addition, since the functionally graded material does not have a boundary surface where the composition of the constituents changes greatly, heat shock and mechanical strength are strong. Therefore, it is possible to bring the sealing portion for welding the closing body to the closing tube close to the arc tube which becomes high in temperature during lighting, and in combination with the fact that the length of the closing body in the axial direction is short,
It has the advantage that the occlusion tube can be shortened. Therefore, the problems of the foil sealing method and the step joining method can be solved.

[0009]

FIG. 3 (A)
As shown in the figure, the closed tube 1 connected to the end of the arc tube 11
2 is closed with the closing body 50 formed of the functionally graded material, first, the core rod 21 of the electrode is inserted into the closing body 50, and the end face 51 of the closing body 50 where the non-conductive component such as silica is rich.
Is closed to the light emitting tube 11, the closing body 50 is fitted into the closing tube 12, and the closing tube 12 near the end face 51 is heated to weld the closing body 50 to the closing tube 12. As shown in FIG. The edge of the end face 51 of the closing body 50 may not be completely welded to the closing pipe 12, and a crack-shaped unwelded portion C may occur. In addition, holes are made from both end surfaces 51 and 52 of the closing body 50 to portions having conductivity, respectively, and a core rod 21 of an electrode and a terminal (not shown) are inserted into each hole and fixed. A discharge lamp in which the terminal 21 is electrically connected to the terminal is also in practical use.
Is not completely welded to the closed tube 12, and a crack-shaped unwelded portion C is likely to occur.

[0010] In principle, the functionally graded material allows the end face 51 to be made of a 100% non-conductive substance, but in practice it often contains a small amount of metal. For example, SiO ₂
For -mo, several tens ppm in SiO ₂ hundred pp
In some cases, when Mo is mixed and pure silica glass constituting the discharge vessel is fused with silica mixed with Mo, these are less likely to bleed and the above-described crack-shaped unwelded portion C is generated. It will be easier. That is, the generation of the crack-shaped unwelded portion C is a problem that tends to occur when using a functionally graded material.

When a crack-shaped unwelded portion C is formed at the edge of the end surface 51 of the closing body 50, gas which has become high in pressure during lighting enters the unwelded portion C, and stress concentrates on the unwelded portion C. Cracks may progress and the lamp may be damaged.

An object of the present invention is to provide a discharge lamp in which an obstruction formed of a functionally gradient material is completely welded to an obstruction tube and is not damaged during operation.

[0013]

In order to achieve the above object, the present invention provides a discharge vessel made of a non-conductive material, in which a pair of electrodes are opposed to each other and a discharge gas is sealed therein. A cylindrical closed tube formed at the end of the arc tube is formed by mixing non-conductive powder and conductive powder of the same material as the discharge vessel at different ratios continuously or stepwise in the length direction. In a discharge lamp closed with a closure made of a functionally graded material having one end non-conductive and the other end conductive, the discharge lamp is expanded toward the arc tube at the arc tube side end surface of the closure. Then, an opening in which the rim becomes thin is formed.

[0014]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 shows that the rated power is 3
It is a xenon short arc lamp which is kW and is DC-lit, but the discharge lamp of the present invention is not limited to this, and may be a discharge lamp such as a mercury lamp or a metal halide lamp. Further, a long arc type discharge lamp or an AC lamp may be used.

In FIG. 1, a discharge vessel 1 made of quartz glass is used.
The 0 arc tube 11 has a spherical shape or an elliptical spherical shape, and an anode 20 and a cathode 30 made of tungsten are disposed inside the arc tube 11 at an interval of, for example, 5 mm. Xenon gas is sealed at a predetermined pressure as a discharge gas. The closing tubes 12, 12 are connected to both ends of the arc tube 11, and the ends of the closing tubes 12, 12 are closed by a closing body 50 made of a functionally graded material. The functionally graded material used here is a mixture of a powder of the same material as the discharge vessel and a conductive powder, for example, when the discharge vessel is quartz glass, a material obtained by sintering silica powder and molybdenum powder. The mixing ratio is varied continuously or stepwise in the longitudinal direction, one end is made non-conductive and the other end is made conductive. As an example, the non-conductive end face 51 of the closing body 50 is made of almost 100% silica, and the conductive-side end face 5 is made of silica.
2 is made of a composition of SiO ₂ 50% + Mo50%, but the composition ratio is not necessarily limited thereto.

The closing body 50 is, as shown in FIG.
A substantially conical or substantially hemispherical opening 54 is formed in the non-conductive end face 51 and expands toward the arc tube. Therefore, the end face 51 which is the edge of the opening 54 is thin. The closing body 50 is fitted into the closing tube 12 so that the opening 54 is in the direction of the arc tube 11, and the closing tube 12 is heated at a portion of the non-conductive end face 51 to form the closing tube 12 made of quartz glass. Welded to. At this time, since the end face 51 is thin, the heat capacity of this portion is small, and therefore,
When the closed tube 12 is heated, as shown in FIG. 2 (B), the end surface 51 which is the rim of the substantially conical or substantially hemispherical opening 54 is completely melted and welded to the closed tube 12. The crack-shaped unwelded portion C shown in FIG. 3B does not occur.

The core rod 21 of the anode 20 and the core rod 31 of the cathode 30 are also made of molybdenum rods, are inserted through axial through holes 53 formed in the closing body 50, and protrude from the closing body 50. Then, at the conductive end face 52 of the closing body 50, as shown in FIG. The coefficient of thermal expansion of the conductive end face 52 of the closing body 50 is close to the coefficient of thermal expansion of the core rods 21 and 31 made of molybdenum, and the core rod 21, the core rod 31 and the closing body 50 can be securely fixed. . In the above-described embodiment, the discharge lamp of the sealed type in which the closed tubes 12 and 12 are continuously provided at both ends of the arc tube 11 has been described. However, the closed tube 12 is continuously provided at one end of the arc tube 11. The discharge lamp may be a one-end sealed type discharge lamp. In addition, as the non-conductive powder of the functionally gradient material, in addition to the silica powder described above, when the discharge vessel is made of ceramic, the ceramic powder is used. Of course, other than the molybdenum powder, it is a matter of course that an appropriate metal conductive material powder such as nickel and tungsten can be used.

As described above, since the end surface 51 of the closing body 50 is completely melted and welded to the closing tube 12, no crack-like unwelded portion is generated, so that the crack propagates from this portion during lighting and breaks. Nothing.

[0019]

As described above, in the discharge lamp of the present invention, the closed tube of the discharge vessel is made of a closed body made of a non-conductive powder of the same material as the discharge vessel and a functionally graded material formed of conductive powder. In addition to the closing, the opening is formed in the arc tube side end surface of the closing body in the direction of the arc tube to form an opening having a thinner rim. Thus, the discharge lamp can be prevented from being damaged.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an enlarged explanatory view of a main part.

FIG. 3 is an explanatory diagram of a conventional example.

DESCRIPTION OF SYMBOLS 10 Discharge vessel 11 Arc tube 12 Closure tube 20 Anode 21 Anode core bar 30 Cathode 31 Cathode core bar 50 Closure body 51 Non-conductive component-rich end surface 52 Conductive component-rich end surface 53 Penetration Hole 54 substantially conical or substantially hemispherical opening 60 metal wax

Claims (1)

[Claims] 1. A discharge vessel made of a non-conductive material has a pair of electrodes opposed to each other and a discharge gas sealed therein, and a cylindrical closed tube formed at an end portion of the discharge tube includes: A non-conductive powder and a conductive powder of the same material as the discharge vessel are continuously or stepwise mixed at different ratios in the length direction and molded, and one end is made non-conductive and the other end is made conductive. In a discharge lamp closed by a closing body made of a functionally graded material, an opening is formed on an arc tube side end surface of the closing body in a direction toward the arc tube to form an opening having a thinner rim. And discharge lamp.