JP4900870B2 - Discharge lamp, projection light source device using the discharge lamp, and image projection device - Google Patents

Description

The present invention relates to a discharge lamp and a light source device equipped with the discharge lamp, and more particularly to processing of an electrode mainly made of tungsten used in the discharge lamp and improvement of the electrode structure.

Today, high-pressure mercury lamps, high-pressure sodium lamps, metal halide lamps, xenon lamps, ultra-high-pressure mercury lamps, UV lamps, flash lamps, i-ray lamps and other discharge lamps are used not only for general lighting but also for solar radiation devices and insecticides. It is used for various purposes such as growth, sterilization and projector backlights, and is indispensable for our daily lives. However, in recent years, demands for higher efficiency and maintenance of characteristics of discharge lamps (reduction of changes in characteristics such as life extension and color characteristics) have been increasing due to demands for energy saving.

In general, most of the discharge lamps have a pair of electrodes made of at least tungsten, and specific light is obtained by discharging between the electrodes. However, in these discharge lamps, blackening of the arc tube bulb due to sputtering of the electrode material, cracks in the seal portion due to the difference in thermal characteristics between the electrode core on the back side of the electrode buried in the arc tube seal portion and the glass, etc. A malfunction occurs. In addition, in a discharge lamp to which a metal halide is added, the metal halide enters the gap between the seal portions at the back of the electrode, and reacts with the electrode material or deposits as it is, so that a significant color change occurs during the lifetime.

As described above, these defects are often caused by electrodes, and improvements in efficiency and life are attempted by improving these electrodes.
For example, by forming a thicker electrode part than the electrode core on the discharge space side of the electrode core and integrating it with the coil wound around the electrode core behind the electrode core, heat dissipation of the electrode The lifetime is improved by suppressing evaporation of the electrode material due to excessive temperature rise of the electrode part. In addition, a method that can manufacture such an electrode at a low cost has been proposed. (For example, see Patent Document 1)
JP 10-92377 A (Toshiba Lighting & Technology)

In order to keep the temperature of each part of the electrode appropriately, there has been proposed a method for solving the problem by having a stepped portion with a reduced cross-sectional area and a tapered tapered portion at the rear part of the electrode. (See Patent Document 2) This can obtain a stable and efficient discharge by the heat storage effect of the electrode and the appropriate heat dissipation effect of the tip when the lamp is turned on. In addition, since the electrode core embedded in the arc tube seal does not require high-temperature operation with respect to the electrode tip, the heat from the electrode tip to the electrode rear can be reduced by reducing the diameter of a part of the electrode rear. Conduction can be suppressed, heat generated by discharge can be prevented from escaping to the rear portion of the electrode, and the temperature of the sealing portion can be lowered. Furthermore, it is possible to suppress the rupture caused by stress due to the difference in thermal expansion coefficient between the electrode rear part buried in the sealing part, the metal foil and the bulb glass, or the intrusion of the encapsulated material due to insufficient adhesion.
JP 2003-346708 A (Toshiba Lighting & Technology)

From the description and the shape of the disclosed electrode processing method, it is considered that the electrode is manufactured by a general cutting process conventionally used in a tungsten processing method. However, cutting is very expensive and takes a long time. In addition, tungsten is recrystallized by applying heat to the tungsten that is processed during processing, resulting in a decrease in strength. When an electrode is used for a discharge lamp, there is a problem that the electrode is broken when vibration or the like is applied during the manufacturing process of the discharge lamp or as a product.

  Moreover, the electrode core rod also shown in the drawing of Patent Document 2 has a corner portion of a step portion. For this reason, there is a high possibility that the point at which discharge is started at the time of starting the lamp is not the tip of the electrode but a step portion at the rear of the electrode, which causes a back arc. As a result, there is a problem that electrode sputtering or rupture is likely to occur.

  Furthermore, when producing the arc tube, the quartz tube, which is the arc tube material, is heated and the metal material such as the electrode is hermetically sealed by pressure sealing. Even if it has a tapered part with taper, if the degree of reducing the cross-sectional area is large, it may be broken during the crimping sealing process, and conversely if the degree of reducing the cross-sectional area is small, the electrode Effects such as a heat storage effect and an improvement in the airtightness between the electrode core dedicated part at the time of pressure sealing and the metal foil and the glass of the arc tube (bulb) cannot be obtained. Therefore, in order to improve the characteristics and life by reducing the diameter of the rear part of the electrode, the effect cannot be obtained unless the diameter of the electrode is reduced within a certain appropriate range.

Also, the length of the electrode core rod sealed to the seal portion is one of important factors. Even if the electrode diameter is reduced within a certain appropriate range, if the length of the electrode core rod sealed to the seal portion is too long, the heat dissipation effect of the seal portion increases, and the heat storage effect of the electrode tip portion increases. It can no longer be obtained. On the other hand, if the length of the electrode core rod sealed to the seal portion is too short, there is a high possibility that the electrode will break when vibration or the like is applied. Therefore, not only the diameter of the electrode core but also the length of the electrode core sealed to the seal portion is not within an appropriate range, and the effect cannot be obtained.

In addition to this, a method for reducing the roughness of the surface of the electrode tip and the electrode rear part (contact portion of the arc tube bulb) by composite electrolytic polishing that can be processed in a short time and places little burden on the electrode is disclosed. . By doing so, it is possible to prevent cracks and the like in the seal portion and to improve the life (defective rate). (For example, see Patent Document 3)
Japanese Patent No. 3447706 (NEC microwave tube)

However, since the diameters of the electrode tip and the electrode back are almost the same, the temperature of the electrode tip and the back end cannot be maintained appropriately, and the heat conduction from the electrode tip to the electrode back is large. The temperature of the rear part becomes high, and problems such as cracks in the seal part and reaction with halides cannot be denied.

As described above, proposals have been made to improve the problems of the discharge lamp by processing and treating the electrodes, but the improvement can be made at a low cost, the strength of the electrodes can be maintained, and the service life can be reduced. It is not enough to improve or improve efficiency. However, due to the recent demand for energy saving and the like, a low-wattage and high-efficiency discharge lamp is desired, and further improvement in characteristics and lifetime are necessary.

The present invention has been made in consideration of the above-described problems. The structure of the electrode used in the discharge lamp, the processing method, and the positional relationship between the electrode and the seal portion are further improved to improve the efficiency and the life. The problem is to obtain a long discharge lamp. Moreover, it is an object to be able to manufacture the electrode at a low cost and to obtain a sufficient strength.

In order to solve the above problems, the present invention seals a pair of electrodes at both ends of the arc tube, and at least the tip of the electrode core sticks into the discharge space of the arc tube and the other end is sealed. In the discharge lamp comprising the arc tube embedded in the portion, the electrode core rod of the at least one electrode is formed with at least a small diameter portion by processing a cylindrical member , and protrudes into the discharge space. From the columnar portion to the end face of the other end portion embedded in the sealing portion, the diameter is gradually reduced without a step in a taper shape by electrolytic polishing, and the taper portion formed on the electrode core rod protruding into the arc tube The maximum diameter (Φ _O ) and the diameter (Φ _T ) of the electrode formed at the boundary between the arc tube sealing portion at the other end and the discharge space have the relationship of Formula 1, and the electrode core rod the total length (L ₀₎ and the length of the other end portion of the buried electrode rod in the arc tube sealing portion of Has L _S) Togashiki 2 relations,
[Formula 1]: 0.3 <Φ _T / Φ _O <0.9
[Formula 2]: 0.2 <L _S / L ₀ <0.8
The polished surface is smoothed.

According to the present invention, the electrode having a small diameter processed on the back portion of the electrode using the electropolishing method has sufficient strength as compared with the conventional cutting method and is manufactured in a very short time and at a low cost. it can. In addition, by using this electrode for a discharge lamp, the above-mentioned problems caused by using an electrode that has been subjected to diameter reduction by a conventional method can be improved, and further, the degree of diameter reduction and the positional relationship can be in an appropriate range. By doing so, it is possible to obtain a discharge lamp with high efficiency and long life.
For the above reasons, it is possible to improve the characteristics of a light source device such as a luminaire or projector incorporating a high-pressure discharge lamp having these effects, and to reduce the number of maintenance times compared to the conventional one by extending the life.

In this example, the tungsten rod used as the electrode core rod is processed with a small diameter, and the strength of the electrode core rod is not reduced compared to the conventional manufacturing method by cutting, and it is shorter and less expensive. Can be processed.
Further, by using the electrode as an electrode of a high-pressure discharge lamp, lamp performance such as efficiency and life can be improved.
Furthermore, by installing this high-pressure discharge lamp in the light source device, an inexpensive light source device with fewer lamp replacements was realized.
Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is an explanatory view showing a method of processing a tungsten rod used as an electrode core according to the present invention,
FIG. 2 is a diagram showing an example of a tungsten rod used as an electrode core that has been subjected to a small diameter machining by an electrolytic polishing method.

A working example of reducing the diameter of the base portion of a tungsten rod used as an electrode core by electropolishing will be described.
In the electrolytic polishing apparatus of FIG. 1, a tungsten rod 1 used as an electrode core having a total length of 15 mm and a diameter of φ0.8 mm is attached to the anode side of the DC power source, and a strip-shaped copper plate 2 is attached to the cathode side. It has been. As the electrolytic solution 3, a 5N sodium hydroxide aqueous solution is used, and a tungsten rod and a copper plate used as an electrode core rod are immersed in the aqueous solution. At this time, the tungsten rod is immersed only in the portion to be reduced in diameter. In this embodiment, a portion to be polished of a tungsten rod having a total length of 15 mm is 8 mm. However, since the electrolytic solution surface of the electropolishing apparatus fluctuates, the portion to be electropolished cannot be made constant and varies. In consideration of this variation, about 7 mm was immersed. Then, as a result of electropolishing by applying a current of 20 A at 30 V for 25 s, the electropolishing of (b) was performed as compared with the electrode core not subjected to electropolishing as shown in FIG. The electrode core was able to be reduced in diameter to a tapered shape in which the processed portion 4 was smooth and the diameter continuously decreased. Moreover, there was no consumption of the electrode end, and the total length was not shortened. The degree of restriction of the tapered portion of the electrode can be controlled by changing the voltage, current, and polishing time of the DC power supply.

In addition, in order to conduct an experiment on strength, a tungsten rod processed to approximately the same size by cutting was prepared for comparison, and an experiment for comparing the strength with a tungsten rod thinned by electrolytic polishing was performed. The end of the tungsten rod that was not thinned was fixed and held horizontal, and when a load was applied perpendicularly to the approximate center of the thinned portion of the tungsten rod, cutting was performed. Compared to the tungsten rod, the tungsten rod processed using the electropolishing method was 10 times or more stronger. This is because when cutting is performed, the tungsten rod is heated by the frictional heat generated in the processing and the strength decreases due to recrystallization, whereas in electropolishing, the tungsten rod can be processed without generating frictional heat. This is because strength reduction due to recrystallization does not occur.

Next, a cost comparison for processing one piece to reduce the diameter of the tungsten rod was performed. However, since the processing time for electrolytic polishing is shorter than the cutting processing, the cost can be reduced. At this time, it is possible to reduce the processing time by increasing the rotation speed of the processing machine used for cutting and the contact pressure of the cutting tool, but in that case, the frictional heat is further increased, so the strength is further reduced. It has been found.

From the above, it has been found that the process of reducing the diameter of a tungsten rod used as an electrode core by electropolishing can be produced at a lower cost and in a shorter time than conventional cutting processes, and the strength is increased. Furthermore, it was found that the processed part by electropolishing was uniform and smooth with no traces remaining as compared with the cutting process. Also, the boundary between the large diameter portion and the processed portion generated by the cutting process was smooth without a corner, and had a tapered shape with a continuously decreasing diameter.

Next, an embodiment in which an electrode using a thinned tungsten rod produced by the machining method of the present invention as an electrode core rod is used as a main electrode of a high-pressure discharge lamp will be described.
FIG. 3 is a schematic plan view showing an embodiment of a general illumination discharge lamp according to the present invention. In this embodiment, a metal halide lamp having a rated power of 400 W and including a nonlinear ceramic capacitor 6 (referred to as FEC) as a starter is shown.

As shown in FIG. 3, the high-pressure discharge lamp 5 is a quartz arc tube 7 having a substantially cylindrical discharge space having a maximum outer diameter φ22 mm, a maximum inner diameter φ20 mm, and an internal volume of 1.4 × 10 ⁴ mm ^3. In the discharge space, main electrodes 8a and 8b having the same shape are arranged to face each other with a distance of 43 mm, and an auxiliary electrode 9 is sealed close to one main electrode 8a. 60 mg of mercury and a rare gas (argon) are about 2 kPa (at room temperature) and about 40 mg of metal halides such as scandium iodide are enclosed. Further, heat retaining films 10a and 10b are attached to the outer peripheral portions of the main electrode at both ends of the arc tube 7. Such an arc tube 7 is held in an outer bulb 12 made of hard glass having a bulging portion having a maximum outer diameter of about 116 mm in a central portion in which an appropriate amount of nitrogen having a base 11 called E39 is sealed at one end.

In the outer sphere, an internal starter 6 composed of a non-linear ceramic capacitor (FEC) for generating a starting voltage at the time of starting the lamp, a voltage generated by the internal starter, a current flowing through a circuit in the lamp, and the like. Three resistors 13 for control are connected.

FIG. 4B is an enlarged view of the pair of main electrodes 8a and 8b having the same shape. For comparison, (a) shows an enlarged view of an electrode not subjected to electropolishing. The electrodes 8a and 8b each have an electrode core rod made of a tungsten rod having a small diameter and a length of 15 mm and a diameter (Φ _O ) of 1.0 mm. ing. Of this electrode core, about 8 mm on the rear side of the electrode was electropolished to reduce the diameter. Of the approximately 8 mm subjected to electrolytic polishing, 4.5 mm is sealed to the arc tube. The diameter (Φ _O ) of the electrode core not subjected to electropolishing is 1.0 mm, while the diameter (Φ _T ) of the electrode core at the boundary between the discharge space and the seal portion is 0. It was changed to 9 mm, 0.8 mm, 0.7 mm, 0.6 mm, 0.5 mm, 0.4 mm, and 0.3 mm. As a comparison, an electrode that was not processed by electrolytic polishing was prepared. FIG. 5 shows the positional relationship between the electropolishing portion of the electrode described above, the seal position to the arc tube, and Φ _O and Φ _T. Note that the A side is a portion sealed to the arc tube with O as a boundary, and the B side is a discharge space portion.

In addition, a tungsten wire having a diameter of 0.5 is wound at a location 2 mm away from the end on the tip end side of the electrode core rod 14, and is wound on the inside by four turns with loose winding, and on the outside is densely wound. 6 turns to form a coil 15. The gap between the coils 15 is impregnated with scandium oxide.

Such a high-pressure discharge lamp was incorporated in a light source device as a lighting fixture, and a lighting test was conducted with a copper iron ballast. The results are shown in Table 1. However, when the total length of the electrode core rod is L _O and the length of the rear end side of the electrode core rod sealed to the arc tube seal portion is L _S , the lamp has L _O of 15 mm and L _S of 4. As 5 mm, L _S / L _O = 0.3. This is because if L _S / L _O is larger than 0.8, the heat dissipation effect of the electrode core rod on the rear end side sealed to the seal portion becomes large, and the heat storage effect at the electrode tip portion cannot be obtained. In addition, since the result that the electrode breaks when vibration or the like is applied when L _S / L _O is smaller than 0.2 is obtained in an experiment conducted in advance, L _O which is the total length of the electrode core rod is The length L _S , which is the length of the rear end side of the electrode core bar sealed to the arc tube seal portion, is selected within the range satisfying the following formula.
Formula 2 : 0.2 <L _S / L _O <0.8

For each specification, five lamps were prepared and tested, and the brightness in the table was based on the brightness of Comparative Example 1, and a brightness of 5% or more was obtained as ◯. X was not obtained. In addition, the strength was subjected to a drop test. And as a comprehensive evaluation, in the evaluation of brightness and intensity, both were evaluated as ◯, and the others were evaluated as ×.

From the above results,
Formula 1: 0.3 < Φ _T / Φ ₀ <0.9
If it is in the range, good characteristics were obtained. In addition, when Φ _T / Φ ₀ is 0.9 or more, the effect of improving the brightness is hardly obtained, there is no difference from the case where the electrode core bar is not subjected to the small diameter processing, and the effect of improving the characteristics is seen. I can't. On the other hand, when Φ _T / Φ ₀ is 0.3 or less,
It was also found that electrode breakage occurred during lamp operation.

As a result of the life test of the lamp whose overall evaluation was O in the experiment, there was no particular problem at the time of 5000 hours. Table 1 shows the change in color temperature expressed as the ratio of the color temperature after lighting for 5000h and 100h, but it could be 0.9 or more at 5000h.
More
Formula 3 : 0.4 < Φ _T / Φ ₀ <0.8
In this range, there was no particular problem even at 8000 hours, and the color temperature change was 0.9 or more.

Next, in order to confirm the difference in lamp power, electrode core diameter, etc., from a substantially similar structure although the dimensions are different from the 400 W of rated power 100 W (arc length 17 mm, internal volume 1.3 × 10 ³ mm ³ ). The same test as described above was performed using a metal halide lamp. In the arc tube, metal halides are sealed together with mercury and rare gases similar to the above, although the amount is different.

The electrode core used had a core rod diameter of 0.4 mm and a total length of 7 mm. Of this electrode core, about 4.0 mm on the electrode rear end side was electropolished to reduce the diameter. Of the approximately 4.0 mm that has been electropolished, 3 mm is sealed to the arc tube. The diameter (Φ _O ) of the electrode core not subjected to electropolishing is 0.4 mm, whereas the diameter of the electrode core (Φ _T ) at the boundary between the discharge space and the seal portion is defined as The diameter of the electrode core (Φ _T ) is changed to 0.35 mm, 0.3 mm, 0.25 mm, 0.2 mm, 0.15 mm, and 0.1 mm. As a comparison, an electrode that was not processed by electrolytic polishing was prepared. FIG. 5 shows the positional relationship between the electropolishing portion of the electrode described above, the seal position to the arc tube, and Φ _O and Φ _T. Note that the A side is a portion sealed to the arc tube with O as a boundary, and the B side is a discharge space portion.

As shown in FIG. 4 (b), a tungsten wire having a diameter of 0.5 is wound on the inside at a location 0.5 mm from the tip of the electrode core 14 and is wound four turns by loose winding. Is tightly wound for 6 turns. The coil 15 is impregnated with an emitter made of scandia.
Such a high-pressure discharge lamp was incorporated in a light source device as a lighting fixture, and a lighting test was conducted with a copper iron ballast.

The test results are shown in Table 2. However, when the total length of the electrode core rod is L _O and the length of the rear end side of the electrode core rod sealed to the arc tube seal portion is L _S , the lamp has L _O of 7 mm and L _S of 3 mm. , L _S / L _O = 0.43. This is because if L _S / L _O is larger than 0.8, the heat dissipation effect of the electrode core rod on the rear end side sealed to the seal portion becomes large, and the heat storage effect at the electrode tip portion cannot be obtained. In addition, since the result that the electrode breaks when vibration or the like is applied when L _S / L _O is smaller than 0.2 is obtained in an experiment conducted in advance, L _O which is the total length of the electrode core rod is The length L _S , which is the length of the rear end side of the electrode core bar sealed to the arc tube seal portion, is selected within the range satisfying the following formula.
Formula 2 : 0.2 <L _S / L _O <0.8

For each specification, five lamps were prepared and tested, and the brightness in the table was obtained with a brightness of 5% or more obtained as a reference based on the brightness of Comparative Example 2. Those that do not have a cross. In addition, the strength was subjected to a drop test. And as a comprehensive evaluation, in the evaluation of brightness and intensity, both were evaluated as ◯, and the others were evaluated as ×.

From the above results, as in the previous experiment,
Formula 1: 0.3 < Φ _T / Φ ₀ <0.9
If it is in the range, good characteristics were obtained.
As a result of the life test of the lamp whose overall evaluation was O in the experiment, there was no particular problem at the time of 5000 hours, and the color change at 5000 h was 0.9 or more.
Furthermore, the formula _{3: 0.4 <Φ T / Φ} 0 <0.8
In this range, there was no particular problem even at 8000 hours, and the color temperature change was 0.9 or more.

Next, an embodiment of a light source device used for a projector will be described.
FIG. 6 shows an optical device used as a light source device of a projector, which is a lamp unit 16 in which a high-pressure discharge lamp 17 such as an ultra-high pressure mercury lamp is arranged on the optical axis of a reflecting mirror 18.

As shown in FIG. 6, the high-pressure discharge lamp 17 is made of an arc tube made of quartz glass, and is formed in a discharge space having a maximum outer diameter of about 10 mm, a maximum inner diameter of about 4.5 mm, and an internal volume of about 60 mm ³ formed at the center. In addition, a pair of electrodes 19 having the same shape are arranged to face each other at a distance of 1.0 mm, mercury is about 0.18 mg / mm ³ , and a starting auxiliary gas is a rare gas (argon) is about 20 kPa (at room temperature) and a very small amount of halogen to prevent blackening are enclosed, and the rating is 150 W.

Each electrode 19 is connected to a power supply lead wire via a molybdenum foil 21 embedded in a sealing portion 20 that hermetically seals both ends of the discharge space, and lamp power is supplied from the lighting device through the lead wire. It comes to be supplied.

FIG. 7B is an enlarged view of the pair of electrodes 19 having the same shape shown in FIG. For comparison, (a) shows an enlarged view of an electrode not subjected to electropolishing. The electrode 19 has a length of 8 mm and a diameter of 0.7 mm made by using the above-described tungsten processing method. Of this electrode core, about 6 mm on the electrode rear end side is electropolished to reduce the diameter. Of the approximately 6 mm that has been electropolished, 3.5 mm is sealed to the arc tube. The diameter (Φ _O ) of the electrode core not subjected to electropolishing is 0.7 mm, whereas the diameter of the electrode core at the boundary between the discharge space and the seal portion (Φ _T ) The diameter of the electrode core (Φ _T ) is changed to 0.6 mm, 0.4 mm, and 0.2 mm. As a comparison, an electrode that was not processed by electrolytic polishing was prepared. FIG. 5 shows the positional relationship between the electropolishing portion of the electrode described above, the seal position to the arc tube, and Φ _O and Φ _T. Note that the A side is a portion sealed to the arc tube with O as a boundary, and the B side is a discharge space portion.

A coil portion 23 is formed by winding a tungsten wire having a diameter of φ0.26 mm around the electrode tip portion seven times. Further, the electrode core bar 22 and a part of the coiled tungsten wire are melt processed so as to be integrally welded.

For comparison with the lamp unit 16 described above, this example and a lamp unit in which only the diameter of the thin diameter portion of the electrode core bar was changed were incorporated into a projector for evaluation.
For each specification, five lamps were prepared and tested, and the evaluation criteria were the same as in the above experiment.
The results are shown in Table 3. However, when the total length of the electrode core rod is L _O and the length of the rear end side of the electrode core rod sealed to the arc tube seal portion is L _S , the lamp has L _O of 8 mm and L _S of 3. As 5 mm, L _S / L _O = 0.44. This is because if L _S / L _O is larger than 0.8, the heat dissipation effect of the electrode core rod on the rear end side sealed to the seal portion becomes large, and the heat storage effect at the electrode tip portion cannot be obtained. In addition, since the result that the electrode breaks when vibration or the like is applied when L _S / L _O is smaller than 0.2 is obtained in an experiment conducted in advance, L _O which is the total length of the electrode core rod is The length L _S , which is the length of the rear end side of the electrode core bar sealed to the arc tube seal portion, is selected within the range satisfying the following formula.
Formula 2 : 0.2 <L _S / L _O <0.8

As in the previous experiment, the expression 1: 0.3 < Φ _T / Φ ₀ <0.9
Within the range, there were no problems in strength and brightness, and good characteristics were obtained.
In addition, as a result of performing a life test of the lamp which had no problem in the experiment, there was no problem in use at the time of 3000 hours.
Furthermore,
Formula 3 : 0.4 < Φ _T / Φ ₀ <0.8
Within the range, there was no problem in use even at 5000 hours, and good results were obtained.
From the above, it was possible to obtain a discharge lamp with high efficiency and long life by using a tungsten rod mainly made of tungsten with a small-diameter portion formed within the scope of the present invention as an electrode core rod of the discharge lamp. Further, in the processing method of the present invention, a tungsten rod having a reduced diameter can be manufactured at a low cost, and further sufficient strength can be obtained.

The present invention is not limited to general illumination discharge lamps and projector discharge lamps, but can be applied to discharge lamps for other purposes. The same effect can be obtained with a tungsten rod containing a few percent or less of thorium oxide, cerium oxide, or the like.

The electrode of the present invention can be used in various discharge lamps such as a general illumination lamp and a special lamp.

It is a front view which shows explanatory drawing embodiment which shows the processing method of tungsten which concerns on this invention. It is a figure which shows the example of the processed tungsten rod (electrode core rod). 1 is a schematic plan view showing an embodiment of a discharge lamp for general illumination according to the present invention. It is an enlarged view of the pair of main electrodes 15a, 15b having the same shape. The figure which shows the positional relationship when the electrode which performed the electric field polishing was mounted | worn with the arc tube. Another embodiment of a lighting apparatus using an optical device used as a light source device of a projector. The enlarged view of the electrode of this invention of the lamp | ramp used for a projector.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tungsten stick 2 Copper plate 3 Electrolyte 4 Processing part 5 High pressure discharge lamp 6 Starter 7 Light emission tube 8a, 8b Electrode 9 Electrode 10a, 10b Thermal insulation film 11 Base 12 Outer sphere 13 Resistance 14 Electrode core 15 Coil part 16 Lamp unit 17 High pressure discharge lamp 18 Reflector 19 Electrode 20 Sealing part 21 Molybdenum foil 22 Electrode core rod 23 Coil part

Claims (4)

A discharge lamp comprising a pair of electrodes sealed at both ends of an arc tube, the electrode comprising an arc tube in which at least the tip of the electrode core bar protrudes into the discharge space of the arc tube and the other end is embedded in the seal portion The electrode core rod of the at least one electrode has at least a small-diameter portion formed by processing a cylindrical member, and is embedded in the sealing portion from the cylindrical portion protruding into the discharge space. The end surface of the other end portion is gradually reduced to a taper-shaped step by electrolytic polishing without any step , and the maximum diameter (Φ _O ) of the tapered portion formed on the electrode core rod protruding into the arc tube and the other end portion The diameter (Φ _T ) of the electrode formed at the boundary between the arc tube sealing portion and the discharge space has the relationship of Formula 1, and the total length (L ₀ ) of the electrode core rod and the arc tube seal And the length (L _S ) of the other end of the electrode core embedded in the portion has the relationship of Formula 2:
[Formula 1]: 0.3 <Φ _T / Φ _O <0.9
[Formula 2]: 0.2 <L _S / L ₀ <0.8
A discharge lamp characterized in that the polished surface is smoothed.
A projection light source device comprising the discharge lamp according to claim 1 and a concave reflecting mirror.
An image projection apparatus using the discharge lamp according to claim 1 as a light source device.
An image projection apparatus used as the light source apparatus according to claim 2.