JP4797790B2 - Discharge lamp - Google Patents

Description

  The present invention relates to a discharge lamp, and more particularly to a discharge lamp used in an exposure apparatus for forming a pattern such as a semiconductor, a liquid crystal panel, and a printed wiring board, and a discharge lamp used as a light source for a projector, a projector, and the like.

  Conventionally, an exposure apparatus for forming a pattern of a semiconductor, a liquid crystal panel, a printed wiring board, or the like, or a discharge lamp used as a light source for a projector or a projector, has a sealing tube connected to both ends of the arc tube forming a light emitting space. And a pair of electrodes are arranged so as to oppose each other in the bulb, and, for example, rare gas and mercury are sealed therein. From the electrode support rod extending along the tube axis toward the arc tube.

  In addition, as a means for fixing the electrode to the insertion portion of the electrode support rod, for example, as described in JP-A-2001-23566, a recess is formed so as to open at the end of the electrode, and a metal is formed in the recess. Means for holding the insertion portion of the electrode support rod through the foil are known.

  FIG. 7 is a cross-sectional view showing an electrode 13 and an electrode support bar 15 of a conventional discharge lamp. A tapered concave portion 14 is formed so as to open to the end portion 13a of the electrode 13 and have a diameter slightly smaller toward the tip of the electrode 13, and the insertion portion 15a of the electrode support rod 15 is formed as the concave portion 14 of the electrode 13. In other words, it is processed into a tapered shape so that the diameter is slightly smaller toward the tip, and a metal foil 16 is formed on the peripheral surface of the insertion portion 15a.

  Further, the insertion portion 15 a of the electrode support rod 15 is inserted into the recess 14 of the electrode 13, and the insertion portion 15 a of the electrode support rod 15 is press-fitted so that the whole is accommodated in the recess 14 of the electrode 13. The foil 16 is between the insertion portion 15 a and the recess 14, and the insertion portion 15 a of the electrode support rod 15 is inserted and fixed in the recess 13 a of the electrode 13. The taper angle 20 of the concave portion 14 of the electrode 13 and the insertion portion 15a of the electrode support rod 15 is, for example, a shape that is shifted 0.06 mm in the radial direction when it advances 20 mm in the axial direction, that is, 0.09 °.

  However, when the electrode support bar 15 is inserted in contact with the electrode 13 at a substantially vertical surface, as in the case where the taper angle 20 is 0.09 °, the radial dimension of the electrode 13 or the electrode support bar 15 is small. The error becomes a large dimensional error in the axial direction. FIG. 8 is a diagram showing the influence of the dimensional error in the radial direction of the electrode 13 and the electrode support rod 15 on the axial dimension. As shown in FIG. 8A, when the diameter of the recess 14 of the electrode 13 is slightly small, or when the diameter of the insertion portion 15a of the electrode support bar 15 is slightly large, the electrode 13 and the electrode support bar 15 are inserted. Can not do it. 8B, when the diameter of the recess 14 of the electrode 13 is slightly large, or when the diameter of the insertion portion 15a of the electrode support bar 15 is slightly small, the electrode 13 and the electrode support bar 15 May be greatly displaced in the axial direction, resulting in a dimensional error, and may not be fixed.

  Therefore, a molybdenum foil, a tantalum plate or the like is wound around the insertion portion 15a of the electrode support rod 15, and the thickness of the metal foil 16 is adjusted by repeated trial and error. The dimensional error in the radial direction of the electrode 14 and the electrode support bar 15 is corrected by adjusting the thickness, the number of windings, and the position of the metal foil 16 to cancel the dimensional error in the axial direction.

However, the holding force of the electrode 13 by the electrode support bar 15 is a frictional force generated when the metal foil 16 pushes the insertion portion 15 a and the electrode 13 of the electrode support bar 15 by the elastic force of the metal foil 16. Therefore, the holding force of the electrode 13 by the electrode support bar 15 varies depending on the thickness of the metal foil 16, so that the holding force differs between products, resulting in large variations. Japanese Patent Application Laid-Open No. 2001-23566 describes that the holding force of the electrode 13 by the electrode support rod 15 is 40 kgf to 250 kgf when pulled out by 1000 kgf. If the electrode mass increases due to an increase in the electric power applied to the discharge lamp, a larger holding force than before is required, and when the holding force of the electrode 13 by the electrode support bar 15 becomes small due to variations, the discharge lamp is being transported. Alternatively, the electrode 13 may fall off the electrode support rod 15 during lighting.
JP 2001-23566 A

  The present invention has been made on the basis of the circumstances as described above, and an object thereof is to insert an electrode support rod through a metal foil into the recess of the electrode, and to have excellent dimensional accuracy in the axial direction. An object of the present invention is to provide a discharge lamp in which the holding force of an electrode by a support rod does not vary between products and can be held reliably.

  In the present invention, in the discharge lamp in which the electrode support rod is inserted into the recess of the electrode via the metal foil, the recess of the electrode is tapered toward the inner side of the electrode, and the insertion portion of the electrode support rod is also at the tip. The taper is such that the diameter becomes smaller as it goes, the two taper angles are the same angle, and the taper angle is θ ≧ 0.8 °.

  The dimensional accuracy in the axial direction is improved by setting the taper angle of the recessed portion of the electrode and the insertion portion of the electrode support rod to θ ≧ 0.8 °. In addition, it is possible to provide a discharge lamp that supports an electrode on the insertion portion of the electrode support rod with a stable holding force between products, and can hold the electrode reliably without variation in the holding force.

Below, the discharge lamp of this invention is demonstrated based on drawing.
FIG. 1 is an explanatory sectional view showing an outline of a configuration of an example of a discharge lamp according to the present invention. The bulb 10 in this discharge lamp is made of quartz glass, and includes an elliptical arc tube 11 and a sealing tube 12 that is continuously provided so as to extend outward from both ends of the arc tube 11.

  Inside the arc tube 11 of the bulb 10, electrodes 13 made of tungsten are arranged so as to face each other, and are supported at the tip of a cylindrical electrode support rod 15 made of tungsten.

  An arc tube 11 of the bulb 10 is filled with a noble gas such as xenon, argon, krypton, or a mixture thereof, and, if necessary, a luminescent material such as mercury.

  The pressure of the sealed gas is, for example, 0.1 to 10 atm at the time of sealing. When mercury is used as the luminescent material, the amount of sealed gas is, for example, 0.5 by weight per inner volume of the arc tube 11 in the bulb 10. ~ 60 mg / cc.

The state which an electrode support rod hold | maintains to an electrode using FIG. 2 is demonstrated.
The electrode 13 has, for example, an outer diameter of 10 mm or more, a length of 10 mm or more, and a mass of 100 g or more, and has a recess 14 that opens at the end 13a. The concave portion 14 forms a columnar fitting insertion portion having a taper that decreases in diameter toward the tip, on the inner side of the electrode. The taper angle 20 of the recess 14 of the electrode 13 refers to how much the taper continuing from the end 13a is inclined from the vertical direction. Further, the electrode support rod 15 has a diameter of, for example, 2 mm or more, and is processed into a taper such that the diameter decreases as the insertion portion 15a at the distal end moves toward the distal end. The taper angle 20 of the insertion portion 15a of the electrode support bar 15 refers to the angle of how much the taper continuing from the tip of the electrode support bar 15 is inclined from the vertical direction. Further, the taper angle 20 of the concave portion 14 of the electrode 13 and the taper angle 20 of the insertion portion 15a of the electrode support rod 15 are substantially the same angle.

  An electrode support rod 15 is inserted into the recess 14 of the electrode 13 via a metal foil 16. The metal foil 16 is made of a tantalum foil or a molybdenum foil, and is not limited to a shape. However, as shown in FIG. Such a C-shaped cross-sectional shape also has an effect of extracting internal gas. Due to the ductility of the metal foil 16 itself, when the electrode support rod 15 is inserted into the recess 14 of the electrode 13 and press-fitted, the press-fitting load is prevented from being applied to a certain point of the electrode 13 and the electrode 13 is not cracked. ing.

  The fitting tolerance x between the insertion portion 15a of the electrode support bar 15 and the recess 14 of the electrode 13 depends on the processing accuracy of the shaft diameter of the electrode support rod 15 and the hole diameter of the recess 14 of the electrode 13, and the accuracy depends on JIS standards. It has been established. In the case of press-fitting of a clearance spring, for example, when the shaft diameter of the electrode support rod 15 is 6 mm or 8 mm, JIS standard JIS B0401-2 "Dimensional tolerance and fitting method Part 2: Hole and shaft tolerance grade and dimensional tolerance Table "When machining with the strictest accuracy in P11 (hole tolerance) and P28 (shaft tolerance), the shaft diameter tolerance is -0.001mm, the hole diameter tolerance is + 0.001mm, and the fit tolerance x is 0.002 mm at the maximum.

  Further, the axial dimension error y has a relation of axial dimension error y = (fitting tolerance x) / tan θ from a trigonometric function when the taper angle 20 is θ. In the graph of FIG. 4, the horizontal axis indicates the taper angle 20 and the vertical axis indicates the dimensional error y in the axial direction. When machining with strict accuracy using electrolytic polishing or the like, that is, when the fitting tolerance x is 0.002 mm, the relationship between the taper angle 20 and the axial dimension error y is shown in a, and a precision lathe for mass production The relationship between the taper angle 20 and the dimensional error y in the axial direction is shown in b when the above processing is performed, that is, when the fitting tolerance x is +0.02 mm. As shown in FIG. 4, when the fitting tolerance x is +0.002 mm and the taper angle 20 is 0.09 °, the dimensional error y in the axial direction is 0.67 mm. In order to achieve this axial dimensional error y by machining up to a precision lathe, that is, to satisfy when the fitting tolerance x is +0.02 mm, the taper angle must be 0.8 ° or more. I understand that.

  As shown in FIG. 2, the electrode 13 having the taper angle 20 and the electrode support rod 15 are replaced with the electrode support rod 15 in which the metal foil 16 is wound around the insertion portion 15a of the electrode support rod 15. When a press-fitting load is applied by inserting the metal foil 16, the metal foil 16 is crushed between the insertion portion 15a and the recess 14 because the force with which the electrode support rod 15 presses the electrode 13 is increased by increasing the taper angle 20. The concave portions 14 of the electrodes 13 and the insertion portions 15a of the electrode support rods 15 can be brought into close contact with each other. Since the electrode 13 and the electrode support bar 15 are in close contact, the pressing force of the electrode 13 can be directly transmitted, and the holding force of the electrode 13 by the electrode support bar 15 is not affected by the metal foil 16.

  From the above, even if the fitting tolerance x between the electrode support rod 15 and the electrode 3 is increased by setting the taper angle 20 of the recess 14 of the electrode 13 and the insertion portion 15a of the electrode support rod 15 to 0.8 ° or more, Since the displacement in the height direction becomes small, the dimensional error y in the axial direction can be kept within an appropriate range.

  Further, since the pressing force of the electrode 13 can be directly transmitted to the electrode support rod 15 through the metal foil 16, the holding force of the electrode 13 by the electrode support rod 15 does not vary, and the product can be stably held between products. The electrode 13 can be held on the insertion portion of the electrode support rod 15 by force.

Then, the strength test of the holding force of the electrode by the electrode support rod of the discharge lamp of the present invention was performed.
The specifications of the electrodes and electrode support rods used as test objects are shown below.
<Specifications>
Electrode: Made of tungsten, diameter 25 mm, overall length 38 mm, concave maximum diameter 6.2 mm, concave overall length 38 mm
Electrode support rod: made of tungsten, diameter φ6 mm, insertion part total length 25 mm
Metal foil: made of molybdenum Three types of electrodes and electrode support rods were prepared in which the taper angle of the recessed portion of the electrode and the insertion portion of the electrode support rod was 1.1 °, 2.8 °, and 5.7 °. Insert the insertion part of the electrode support rod into the recess of the electrode under a predetermined press-fitting load, and then apply a force to pull out the electrode and the electrode support rod, and apply the force when the electrode support rod comes out of the recess of the electrode. Measured and used as the pull-out strength. The press-fit load was 20 kgf, 50 kgf, 150 kgf, 500 kgf, and 1000 kgf.

  FIG. 5 is a graph showing the strength test results. The abscissa is the press-fit load, the ordinate is the drawing strength, the experimental results are plotted, and approximate curves are drawn for taper angles of 1.1 °, 2.8 °, and 5.7 °, respectively. The inclinations of the approximate curves were 0.57, 0.52, and 0.31, respectively, for taper angles of 1.1 °, 2.8 °, and 5.7 °. From this graph, it was found that the press-fit load and the pull-out strength have a fixed relationship and are uniformly determined at a fixed taper angle. Further, it was found that the larger the taper angle, the smaller the variation between products in the holding force of the electrode by the electrode support rod. As a result, it was found that even when the taper angle was 0.8 ° or more, sufficient holding force was obtained, and variation between products was reduced, so that even a holding force smaller than that of the related art could be reliably held.

  FIG. 6 is a graph showing data obtained from the strength test results of FIG. The horizontal axis is the taper angle, the vertical axis is the drawing strength / indentation load, the data obtained from the strength test results in FIG. 5 are plotted, and an approximate curve is drawn. From this graph, it was found that the pull-out strength with respect to the press-fit load increases as the taper angle is smaller. Further, it was found that when the taper angle is 8 ° or more, the electrode holding force by the electrode support rod does not work.

From the above experimental results, by setting the taper angle to 0.8 ° or more, the machining is completed up to the precision lathe, and even when the fitting tolerance x is +0.02 mm, the axial dimension error is 0.67 mm. Thus, it was confirmed that the axial dimensional accuracy was improved, the electrode holding force of the electrode support rod was less varied between products, and could be held securely.

Schematic sectional view of the discharge lamp of the present invention Enlarged sectional view of the discharge lamp of the present invention The perspective view of the metal foil of the discharge lamp of this invention Relationship diagram of axial dimension error to taper angle and opening diameter tolerance Relationship between press-fit load and pull-out strength Relationship between taper angle and pull-out strength / press-fit load Expanded sectional view of a conventional discharge lamp Expanded sectional view of a conventional discharge lamp

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Bulb 11 Light-emitting tube 12 Sealing tube 12a Narrowing part 13 Electrode 13a End part 14 Recess 15 Electrode support rod 15a Insertion part 16 Metal foil 20 Taper angle

Claims (1)

In the discharge lamp in which the electrode support rod is inserted through the metal foil in the recess of the electrode,
The concave portion of the electrode has a taper that narrows toward the inner side of the electrode, and the insertion portion of the electrode support rod also has a taper that has a diameter that decreases toward the tip, and the two taper angles are the same angle, A discharge lamp characterized in that the taper angle is θ ≧ 0.8 °.

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