JP3407555B2 - Light irradiation device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light irradiation device comprising a short arc lamp and a concave reflecting mirror. A short arc lamp such as a xenon lamp or a metal halide lamp has a small light source and is very close to a point light source. Therefore, the arc luminescent spot of the short arc lamp is arranged at the focal position of a concave reflecting mirror. Light emitting devices that emit light are widely used in various fields. In a short arc lamp, a pair of electrodes are arranged opposite to each other at intervals of several mm in a spherical or elliptical arc tube at the center of a quartz glass discharge vessel, and a luminous metal such as mercury and a discharge gas are sealed therein. Is done. Then, a cylindrical closed tube is continuously provided at both ends of the arc tube, and the electrode rod and the external lead rod are closed in a state where they are electrically connected by the closed tube.
Since the electrode rod made of molybdenum and the closed tube made of quartz glass have greatly different coefficients of thermal expansion, the closed tube cannot be closed by welding directly to the electrode bar. For this reason, conventionally, the closed pipe has been closed by a step connection method, a foil sealing method, or the like. [0004] 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 prepared. Are sequentially welded from the end of the closed tube of the discharge vessel to extend the closed tube, and the glass tube at the end closest to the coefficient of thermal expansion of tungsten is welded to the electrode rod. When the number of the intermediate glass tubes is reduced, the difference in the coefficient of thermal expansion between adjacent intermediate glass tubes increases, and the mechanical strength of the joint portion is weak.
It is necessary to increase the number of intermediate glass 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, the molybdenum foil is sandwiched between quartz glasses, and the center of the molybdenum foil is sandwiched. 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. FIG. 5 shows a xenon short arc lamp having a rated power of 3 kW closed by a foil sealing method.
An anode 20 and a cathode 30 are arranged in the arc tube 11 of the discharge vessel 10 to face each other. Blocking tubes 12 and 13 are connected to both ends of the arc tube 11, and caps 41 and 42 are attached to ends of the blocking tubes 12 and 13, respectively. The ends of the core rod 21 of the anode 20 and the core rod 31 of the cathode 30 are connected to the tungsten rods at the portions covered with the bases 41 and 42 by using step connection glass (not shown).
That is, the portion covered by the bases 41 and 42 is the seal portion, and the distance between the arc tube 11 and the seal portion is long. Incidentally, the distance L ₁ from the arc bright spot to the mouthpiece 41 the end of the cathode side is 165mm, the distance L ₂ from the arc bright spot to the mouthpiece 42 the end of the anode side is 185 mm. In the case of a short arc lamp using mercury vapor, if the distance between the arc tube and the seal portion is increased, the temperature of the tube wall at the base of the electrode core becomes low.
The coldest point temperature becomes too low and 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 core rod to keep the temperature. However, there is a problem that light is blocked by the heat insulating film and the light use efficiency is reduced. As described above, according to the step joining method or the foil sealing method, the closing pipe of the short arc lamp is elongated in the axial direction. However, as shown in FIG. A light irradiating device that is fitted and attached to the central opening 91 of the concave reflecting mirror 9, arranged so that the other closed tube 13 extends in the optical axis direction of the concave reflecting mirror 9, and condenses reflected light at a predetermined position. , The closed tube 13 extending in the optical axis direction of the concave reflecting mirror 9 is long.
A part of the reflected light enters the closed portion 13 and is blocked, so that the area of the reflecting surface of the concave reflecting mirror 9 actually used is reduced, and there is a problem that the light use efficiency is reduced. SUMMARY OF THE INVENTION It is an object of the present invention to provide a light irradiating device having a high light utilization efficiency and a high reliability of a closed portion of a short arc lamp. [0010] In order to achieve the above object, an invention according to claim 1 is directed to a spherical or elliptical arc tube formed at the center of a discharge vessel made of a non-conductive material. A short arc lamp having a pair of electrodes opposed to each other and a discharge gas sealed therein, and a cylindrical closed tube formed at each end of the arc tube, and a concave reflecting mirror having a central opening. One of the closed tubes is fitted into the central opening of the concave reflecting mirror, and the other closed tube extends toward the open end of the concave reflecting mirror. non-conductive powder and the conductive powder tube closed tube only discharge vessel of the same material of the other
The mixture is molded continuously and stepwise in different ratios in the axial direction and molded, one end is made non-conductive, and the other end is closed by a closing body made of a functionally graded material made conductive, thereby forming the other end. The occlusion tube is shorter than the one occlusion tube, thereby improving light use efficiency. Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 shows a short arc lamp used in the light irradiation device of the present invention. The short arc lamp is, for example, a xenon short arc lamp whose rated power is 3 kW and is DC-lit. The short arc lamp is not limited to the xenon short arc lamp, but may be a short arc type mercury lamp, a metal halide lamp, or the like. Alternatively, the light may be lit by alternating current. In FIG. 1, a discharge vessel 1 made of quartz glass is shown.
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. Blocking tubes 12 and 13 are continuously provided at both ends of the arc tube 11. The closing tube 12 on the cathode side has the same length as the conventional lamp shown in FIG. Is attached. The core rod 31 of the cathode 30 is made of a tungsten rod, and its end is connected to a tungsten rod (not shown) in a portion covered with the base 41 and is sealed by a step connection method. The anode side closing tube 13 is connected to the cathode side closing tube 12.
The end of the closed tube 13 is closed by a closed 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 52 is made of a composition of 50% SiO ₂ + 50% Mo. It is not limited to. Then, as shown in FIG.
Is fitted into the closed tube 13 so that the non-conductive end face 51 faces the arc tube 11, and the end face 51 is welded to the quartz glass closed tube 13. The core rod 21 of the anode 20 is made of a molybdenum rod, and is inserted into an axial through hole 53 formed in the closing body 50. The metal wax 54 and the coefficient of thermal expansion are hermetically fixed on the conductive end face 52 of the closing body 50 by sealing glass having a coefficient of thermal expansion close to that of molybdenum. The coefficient of thermal expansion of the conductive end surface 52 of the closing body 50 is close to that of the core rod 21 made of molybdenum, and the core rod 21 and the closing body 50 can be securely fixed. As shown in FIG. 1, a contact 4 made of a metal having high oxidation resistance, for example, molybdenum is provided on the end of the core rod 21 protruding from the closing body 50.
The contact 43 is connected to a heat-resistant lead wire 44 made of a stranded wire. Alternatively, as shown in FIG. 3, holes are made from both end surfaces 51 and 52 of the closing body 50 to portions having electric conductivity, and a core rod 21 and an external lead rod 22 are inserted into each hole. May be fixed. Thereby, the core rod 21 and the external lead rod 22 are electrically connected, and the airtightness can be further ensured. In order to securely fix the core rod 21 and the external lead rod 22 to the closing body 50, the core rod 21 and the external lead rod 22 are inserted into the holes of the closing body 50 after the preliminary firing before the main firing of the closing body 50 at a high temperature. Then, it is preferable to harden by firing. Here, the gradient functional material used is such that the ratio of a non-conductive powder such as SiO ₂ and a conductive powder such as Mo changes continuously or stepwise from one end face to the other end face. Therefore, even if the length of the closing body 50 in the axial direction is short, the ratio of SiO ₂ and Mo on one end surface and the other end surface can be largely changed. That is,
With the short plug 50, the thermal expansion coefficient of one end face can be close to that of quartz glass and the thermal expansion coefficient of the other end face can be close to that of molybdenum. Can be closed. Further, since the closing body 50 made of the functionally gradient material formed by sintering the silica powder and the molybdenum powder is resistant to heat shock, the closing body 50 as the sealing portion is heated to a high temperature as in the case of the above-mentioned foil sealing method. It is not necessary to be largely separated from the arc tube 11. Therefore,
The length of the closing tube 13 can be made much shorter than the conventional step joining method or foil sealing method. Incidentally, the distance L ₁ from the arc bright spot to the mouthpiece 41 the end of the cathode side as in the conventional example 165m
is a m, the distance L ₂ from the arc bright spot to the end of the closure 50 on the anode side is 80 mm. Further, the closing body 50 formed by sintering the silica powder and the molybdenum powder has a high mechanical strength and has only two welding points, so that the manufacturing process is simpler than the conventional foil sealing structure. And a highly reliable lamp can be obtained. In addition, as the non-conductive powder of the functionally graded material, other than the above-mentioned silica powder, if the discharge vessel is made of ceramic, the ceramic powder may be used, and the same material as the discharge vessel may be 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 shown in FIG. 4, the short arc lamp 1 is combined with a concave reflecting mirror 9 to form a light irradiation device. That is, the cathode-side closing tube 12 is fitted and fixed in the central opening 91 of the concave reflecting mirror 9, and the arc luminescent spot of the short arc lamp 1 is arranged at the focal position of the concave reflecting mirror 9 to collect light. Since the anode-side closing tube 13 extending to the open end side of the reflecting mirror 9 can be made much shorter than in the conventional example, the ratio of light reflected by the concave reflecting mirror 9 to the closing tube 13 is extremely small, and the light utilization rate is reduced. Can be significantly improved. As described above, according to the light irradiation apparatus of the present invention, only the closed tube on the open end side of the concave reflecting mirror of the short arc lamp is connected to the non-conductive powder such as silica and the molybdenum or the like. By closing with a closing body made of a functionally graded material formed of conductive powder, the closing pipe of the short arc lamp extending to the open end side of the concave reflecting mirror is closed on the side fitted into the central opening of the concave reflecting mirror. Since the length is shorter than the tube, the light irradiating device can have a high light utilization rate and a high reliability of the closed portion of the short arc lamp.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view of a short arc lamp used in a light irradiation device of the present invention. FIG. 2 is an explanatory diagram of a closed portion of a short arc lamp. FIG. 3 is an explanatory view of another embodiment of a closed portion of a short arc lamp. FIG. 4 is an explanatory diagram of light use efficiency of the light irradiation device of the present invention. FIG. 5 is an explanatory view of a conventional short arc lamp. FIG. 6 is an explanatory diagram of light use efficiency of a conventional light irradiation device. DESCRIPTION OF THE SYMBOLS 1 Short arc lamp 10 Discharge vessel 11 Emission tube 12 Cathode side closing tube 13 Anode side closing tube 20 Anode 21 Anode core rod 30 Cathode 31 Cathode core rod 41, 42 Cap 43 Contact point 44 Lead wire 50 Closure body 9 Concave reflector 91 Central opening of concave reflector

Continuation of the front page (56) References JP-A-63-241850 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 61/36 F21V 31/00 G02B 5/10

Claims (1)

(57) Claims 1. A pair of electrodes are opposed to each other in a spherical or elliptical arc tube formed in the center of a discharge vessel made of a non-conductive material, and a discharge gas is provided. Is enclosed, and comprises a short arc lamp in which cylindrical occlusion tubes are formed at both ends of the arc tube, and a concave reflecting mirror having a central opening, and one occlusion tube of the short arc lamp is provided at the central opening of the concave reflecting mirror. In the light irradiation device in which the other closed tube is fitted and the other closed tube extends to the open end side of the concave reflecting mirror, of the closed tube, only the other closed tube on the open end side of the reflecting mirror is made of the same material as a discharge vessel. A non-conductive powder and a conductive powder are continuously or stepwise mixed at different ratios in the tube axis direction and molded, and one end is made non-conductive and the other end is made of a functionally graded material made conductive. By closing with the closing body A light irradiation device, wherein the closed tube is shorter than the one closed tube.