JP6185717B2 - Discharge lamp - Google Patents

Description

  The present invention relates to a discharge lamp used in an exposure apparatus or the like, and more particularly to an electrode structure that encloses a heat transfer body in an internal space formed inside the electrode.

  In a discharge lamp, as the output increases, the tip of the electrode becomes high temperature, and an electrode material such as tungsten melts and evaporates, causing a decrease in lamp output. In order to prevent such overheating of the electrode tip, a sealed space is formed inside the electrode, and a heat transfer body such as gold or silver is enclosed therein. During lighting, the heat transfer body melts and convects. Thereby, the heat of an electrode front-end | tip part is conveyed to the electrode support rod side, and front-end | tip part temperature falls.

  In such an electrode structure, when it is lit for a long time, a high temperature creep deformation may occur at the bottom of the space due to a drastic temperature change in the sealed space due to the convection of the heat transfer body, and the tip of the electrode may burst. In order to prevent this, the bottom surface of the sealed space is entirely curved to relieve internal pressure (see Patent Document 1). Or a plate is arrange | positioned in sealed space and the convection along the circumferential direction is controlled (refer patent document 2).

JP 2005-11564 A JP 2012-28168 A

  In the discharge lamp enclosing the heat transfer body, the thickness at the tip of the electrode is thin in order to increase the heat transport efficiency. That is, the distance between the bottom surface of the internal space and the tip surface of the electrode is short. For this reason, the formation of the curved bottom surface and the arrangement of plates that restrict convection cannot sufficiently cope with the creep deformation problem. In particular, in the case of a high-power discharge lamp, the size of the sealed space increases as the electrode size increases, and a large pressure is applied to the inner bottom surface, resulting in high temperature creep deformation.

  Therefore, an electrode structure that is sufficiently durable even when the discharge lamp is used for a long time and that suppresses the heat at the electrode tip is required.

  The discharge lamp of the present invention includes an electrode pair and a discharge tube in which the electrode pair is disposed, and at least one electrode extends in the axial direction and is a sealed cylindrical internal space in which a heat transfer body is enclosed. Have

  For example, the electrode includes a columnar body portion and a tip portion that tapers from the body portion toward the electrode tip surface where arc discharge occurs.

  In the present invention, the thickness on the electrode tip side is larger than the thickness on the electrode side surface side. In the electrode structure for sealing the heat transfer body, the most important issue is to transport the heat on the electrode tip side, so conventionally, the thickness on the electrode tip side is set smaller than the thickness on the electrode side surface side, This was a prerequisite and essential element of the electrode structure.

  However, when the flow in the sealed space of the heat transfer body is studied, the tip portion is increased by increasing the maximum flow velocity of the heat transfer body that is generated near the electrode support rod (on the opposite side of the tip portion) along the electrode axis. However, it has been found that heat transport can be efficiently performed even when a thick electrode structure is employed. For example, it is possible to configure so that the bottom surface of the internal space is located in the body part.

  As an electrode structure that further increases the maximum flow velocity of the heat transfer body, a flat bottom surface is provided in the internal space, and a reduced diameter surface that is reduced in diameter from the side surface of the internal space toward the bottom surface is formed in the internal space. The formation of the flat bottom surface and the reduced diameter surface does not cause stagnation in the flow of the heat transfer body, and the upward flow along the electrode axis of the heat transfer body starts from the vicinity of the bottom surface to increase the maximum flow velocity. Furthermore, since the tip side wall thickness is large, it can sufficiently withstand the deformation creep phenomenon due to tip overheating.

As a configuration of the reduced diameter surface, a cross-sectional R shape, a tapered shape, or the like can be configured. For example, the internal space has a curved surface having a predetermined radius of curvature as the reduced diameter surface, and the curved surface is formed so as to satisfy the following conditional expression. However, R represents the radius of curvature of the curved surface, and L1 represents the diameter of the internal space.

0.03 ≦ R / L1 ≦ 0.27

In particular, the curved surface can be formed to satisfy the following formula.

0.06 ≦ R / L1 ≦ 0.20

In the internal space, a tapered surface having a predetermined inclination angle can be provided as a reduced diameter surface. The tapered surface may be formed so as to satisfy the following conditions. Here, a represents the inclination angle of the tapered surface with respect to the bottom surface, L1 represents the diameter of the internal space, and L3 represents half of the difference between the diameter of the internal space and the diameter of the bottom surface.

0.03 ≦ L3 / L1 ≦ 0.17
10 ≦ a ≦ 60

  The discharge lamp electrode of the present invention includes a columnar body, a tip that tapers from the body toward the electrode tip, and a sealed cylindrical interior that extends along the axial direction and encloses a heat transfer body. The inner wall has a flat bottom surface and the inner space has a reduced diameter from the inner space side surface toward the bottom surface. It has a surface.

  According to the present invention, an electrode excellent in heat transport efficiency and heat-resistant structure can be provided in a discharge lamp.

It is the top view which showed typically the discharge lamp which is 1st Embodiment. It is a schematic sectional drawing of an anode. It is the figure which showed the flow of the heat exchanger at the time of providing the anode which provided the interior space without a diameter-reduced surface, and the interior space without a flat bottom face. It is the figure which showed the flow of the heat exchanger in this embodiment. It is a schematic sectional drawing of the anode of the discharge lamp which is 2nd Embodiment. It is the graph which showed the change of the electrode tip temperature with respect to R / L1, and the maximum flow velocity. It is the graph which showed the proportional relationship of the maximum flow velocity and the electrode tip part temperature. It is the graph which showed the change of the electrode tip temperature with respect to L1 / L3 and the maximum flow velocity.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a plan view schematically showing a discharge lamp according to the first embodiment.

  The discharge lamp 10 can be used as a light source of an exposure apparatus (not shown) for forming a pattern, and includes a discharge tube (light emitting tube) 12 made of transparent quartz glass. A cathode 20 and an anode 30 are coaxially opposed to the discharge tube 12 with a predetermined interval.

  On both sides of the discharge tube 12, sealing tubes 13A and 13B made of quartz glass are provided integrally with the discharge tube 12 so as to face each other, and both ends of the sealing tubes 13A and 13B are provided with caps 19A and 19B. Has been placed.

  Inside the sealing tubes 13A and 13B, conductive electrode support rods 17A and 17B for supporting the metallic cathode 20 and the anode 30 are disposed, and a metal ring (not shown), a metal foil 16A such as molybdenum, etc. , 16B to the conductive lead rods 15A, 15B, respectively.

  The sealing tubes 13A and 13B are welded to glass tubes (not shown) provided in the sealing tubes 13A and 13B, whereby the discharge space DS in which mercury and a rare gas are sealed is sealed. .

  The lead rods 15A and 15B are connected to an external power source (not shown), and are connected between the cathode 20 and the anode 30 via the lead rods 15A and 15B, the metal foils 16A and 16B, and the electrode support rods 17A and 17B. A voltage is applied to. When electric power is supplied to the discharge lamp 10, arc discharge occurs between the electrodes, and a bright line (ultraviolet light) due to mercury is emitted.

  FIG. 2 is a schematic cross-sectional view of the anode.

  The anode 30 has a structure in which a cylindrical body portion 32 connected to the electrode support rod 17B shown in FIG. 1 and a truncated cone-shaped tip portion 34 are integrally formed. The tip portion 34 has an electrode tip surface 34S perpendicular to the electrode axis E where arc discharge occurs. A cylindrical internal space 40 is formed coaxially along the electrode axis E in the body portion 32, and the internal space 40 is sealed by a lid 42.

  A heat transfer body M having a melting point lower than that of the electrode material such as silver is enclosed in the internal space 40. While the lamp is lit, the heat transfer body M melts and becomes a liquid and convects inside the internal space 40. Thereby, the heat of the electrode front-end | tip part 34 is conveyed to the electrode support rod side and the electrode side surface side, and the electrode front-end | tip part 34 is cooled.

  A flat bottom surface 40B parallel to the electrode tip surface 34S is formed in the internal space 40, and a surface (hereinafter referred to as a curved surface) 40T that decreases in diameter from the side surface 40S toward the bottom surface 40B is formed. . Specifically, the cross-sectional shape of the curved surface 40T is a quadrant with a predetermined radius of curvature. The diameter L2 of the flat circular bottom surface 40B is smaller than the inner diameter L1 of the internal space 40.

  The bottom surface 40 </ b> B of the internal space 40 is located inside the body portion 32 and does not extend to the tip end portion 34. Therefore, the tip end side thickness D2 of the anode 30 is larger than the side face side thickness D1. However, the side wall thickness D1 represents the distance between the side surface 40S of the internal space 40 and the electrode outer surface 32S along the direction perpendicular to the electrode axis E, and the tip side wall thickness D2 is from the bottom surface 40B to the electrode tip surface 34S. Represents the distance to. The tip side thickness D2 is determined to be, for example, twice or more the side surface side inner thickness D1.

The curved surface 40T that connects the side surface 40S and the bottom surface 40B is defined in a shape that increases the flow velocity of the flow accompanying the heat transfer of the heat transfer body M. Specifically, when the curvature radius of the curved surface 40T is R, the ratio between the curvature radius R and the inner diameter L1 of the internal space 40 is determined so as to satisfy the following conditional expression.

0.03 ≦ R / L1 ≦ 0.27 (1)

In particular, in the case of a high output short arc discharge lamp or the like, the curved surface 40T is formed so as to satisfy the following conditional expression in order to further increase the flow rate of the heat transfer body M.

0.06 ≦ R / L1 ≦ 0.20 (2)

  Moreover, the electrode axial direction height of internal space is defined in the range of 1 to 2 times the diameter L1 of internal space, for example. In particular, the height may be set to 1.2 to 1.6 times.

  By forming the internal space 40 in which such a saddle-shaped curved surface is provided on the bottom side, the heat transport efficiency is improved in spite of the relatively large thickness D2 of the electrode tip. Hereinafter, the reason will be described with reference to FIGS.

  FIG. 3 is a diagram showing the flow of the heat transfer body when an anode provided with an internal space without a reduced diameter surface and an internal space without a flat bottom surface are provided. FIG. 4 is a diagram showing the flow of the heat transfer body in the present embodiment.

  The arrows shown in FIGS. 3 and 4 indicate the flow when the heat transfer body M is in convection while the lamp is lit. The heat transfer body M rises at the center along the electrode axis E and descends along the side surface. Most of the heat at the electrode tip is transported to the opposite side by the rise of the heat transfer body M along the electrode axis E.

  In a state where such convection is generated in the internal space 40, the heat transfer body M reaches the maximum flow velocity when it rises to the vicinity of the lid 42. The heat transport efficiency depends on the maximum flow velocity, and the heat transport efficiency increases as the maximum flow velocity increases, and thus the temperature rise at the electrode tip can be suppressed.

  In the present embodiment, an electrode structure is adopted in which the electrode tip side wall thickness of the internal space is larger than the side wall thickness. As a result, the temperature on the tip side becomes high and can sufficiently withstand high-temperature creep deformation, and the tip portion is prevented from bursting. However, in the case of such an electrode structure, the transfer efficiency of heat from the electrode front end surface to the heat transfer body M is not superior to the conventional electrode structure with a thin wall thickness. Therefore, it is more important to increase the maximum flow rate of the heat transfer body M as much as possible and increase the ascent rate.

  However, as shown in FIG. 3, in the electrode structure having a large thickness on the electrode tip side, when the reduced surface is not formed, the flow of the heat transfer body is not smooth near the bottom corner, and stagnation occurs. As a result, the maximum flow velocity of the heat transfer body is reduced, and the heat at the electrode tip cannot be transported efficiently.

  On the other hand, when an internal space is formed in which only the curved surface is formed without having a flat bottom surface, the flow of the heat transfer body gathers in the central portion, so that stagnation occurs near the center of the bottom surface. As a result, the upward flow along the electrode axis E of the heat transfer member is generated starting from a position away from the center of the bottom surface. As a result, the maximum flow velocity on the electrode support rod side is reduced.

  On the other hand, in the present embodiment, in the electrode structure having a large thickness on the electrode tip side, a curved surface having a reduced diameter is provided near the flat bottom surface of the internal space. As a result, stagnation is prevented from occurring near the corner of the bottom surface of the internal space, and upward flow along the electrode axis of the heat transfer body is started from the bottom surface. This makes it possible to increase the maximum flow velocity in the vicinity of the electrode support rod of the heat transfer body upward flow along the electrode axis.

  Thus, according to this embodiment, the sealed internal space 40 is formed inside the anode 30 and the heat transfer body M is enclosed. In the internal space 40, a flat bottom surface 40B is provided in the body portion 32, and the electrode tip side thickness D2 is made larger than the side surface side thickness D1. Then, in the vicinity of the bottom surface of the internal space 40, a curved surface 40T having a reduced radius from the side surface 40S toward the bottom surface 40B and having a curvature radius R in cross-sectional shape is formed.

  Next, the discharge lamp which is 2nd Embodiment is demonstrated using FIG. In the second embodiment, a tapered portion having a constant inclination angle is formed in the internal space.

  FIG. 5 is a schematic cross-sectional view of the anode of the discharge lamp according to the second embodiment.

  The anode 130 includes a body portion 132 and a tip portion 134, and an internal space 140 sealed with a lid 142 is formed. The internal space 140 has a flat bottom surface 140B, and a truncated cone-shaped tapered surface 140T having an inclination angle a (°) with respect to the bottom surface 140B is formed in the vicinity of the bottom surface 140B. Similar to the first embodiment, the tip side thickness D2 of the anode 30 is larger than the side surface thickness D1.

When the length which is half of the difference between the inner diameter L1 of the internal space 140 and the width L2 of the bottom surface 140B is L3, L1 / L3 is determined so as to satisfy the following conditional expression. Further, the inclination angle a is determined in the following range.

0.03 ≦ L3 / L1 ≦ 0.17 (3)
10 ≦ a ≦ 60 (4)

  The range of L3 / L1 indicates the range of the width of the tapered surface 140T, and indicates the extent of the diameter L2 of the bottom surface 140B. In addition, the inclination angle a defines a curved surface shape at the bottom corner of the internal space 140, and the range of the inclination angle a represents a range that is tapered.

  By forming the tapered portion 140T that satisfies the above conditional expression, as in the first embodiment, no stagnation occurs at the bottom side corner of the internal space 140, and the flow of the heat transfer body M flows along the electrode axis. The upward flow starts from the bottom surface 140B, and the maximum flow velocity increases.

  A reduced diameter surface other than those in the first and second embodiments may be formed in the internal space. Moreover, you may make it a bottom face of internal space be located in the front-end | tip part side.

  Hereinafter, examples according to the first and second embodiments will be described with reference to FIGS. There, it was verified by simulation how the shape of the internal space based on the above equations (1) to (4) affects the temperature of the electrode tip and the maximum flow velocity of the heat transfer body.

  The discharge lamp of Example 1 includes an anode in which an internal space having a curved surface is formed. The inner space diameter (electrode inner diameter = L1) is 30 mm, the anode diameter (electrode outer diameter) is 40 mm, the inner space bottom surface diameter (L2) is 10 mm, the tip side wall thickness (D2) is 10 mm, and the side wall wall thickness ( An anode with a D1) of 5 mm and an internal space height of 35 mm was modeled, and the tip temperature and maximum flow velocity were simulated by a computer based on the amount of heat assuming an electric power of 14 kW.

  At this time, the electrode tip temperature and the maximum flow velocity were calculated while changing the ratio R / L1 between the radius of curvature R and the inner diameter L1 (= 30 mm). However, the maximum flow velocity represents the flow velocity measured near the electrode support rod side of the heat transfer body rising along the electrode axis.

  FIG. 6 is a graph showing changes in electrode tip temperature and maximum flow velocity with respect to R / L1. FIG. 7 is a graph showing a proportional relationship between the maximum flow velocity and the electrode tip temperature.

  As shown in FIG. 7, it can be seen that the electrode tip temperature decreases as the maximum flow rate increases. Therefore, by defining the range of R / L1 where the maximum flow velocity in FIG. 6 is relatively large, an electrode that lowers the electrode tip temperature can be configured.

  As shown in FIG. 6, the maximum flow velocity increases from around R / L1 = 0.03 and is relatively large up to around 0.27. Such a range of R / L1 coincides with the range of the above formula (1). In particular, the range in which the maximum flow rate is maintained at a high level is 0.06 to 0.20, which matches the range of the above equation (2). Thus, it can be seen that an electrode having an internal space satisfying the above expressions (1) and (2) exhibits an excellent heat transport effect.

  The discharge lamp of Example 2 includes an anode in which an internal space having a tapered surface is formed. Modeling an anode with an internal space diameter of 30 mm, an anode diameter of 40 mm, a bottom surface diameter of 10 mm, a tip side wall thickness of 10 mm, a side wall thickness of 5 mm, and an internal space height of 35 mm, and assuming a power of 14 kW Based on the above, a computer simulation was performed.

  At this time, the electrode tip temperature and the maximum flow velocity were calculated while changing the ratio L1 / L3 between the diameter L1 of the internal space and the one-side width L3 of the tapered surface. However, the inclination angle “a” of the tapered surface is set in a range of 10 ° to 60 °, and is 45 ° here.

  FIG. 8 is a graph showing changes in electrode tip temperature and maximum flow velocity with respect to L1 / L3.

  As shown in FIG. 8, the range of L1 / L3 where the maximum flow velocity is relatively large is 0.03 to 0.17, which coincides with the range satisfying the above expression (3). Therefore, it is confirmed that an electrode having an internal space satisfying the above expressions (3) and (4) exhibits an excellent heat transport effect.

DESCRIPTION OF SYMBOLS 10 Discharge lamp 30 Anode 32 Body part 34 Tip part 34S Electrode tip surface 40 Internal space 40B Bottom surface 40T Curved surface (reduced diameter surface)
140B Bottom 140T Tapered surface (Reduced diameter surface)
D1 Side wall thickness D2 Tip wall thickness

Claims (6)

An electrode pair ;
A discharge tube having the electrode pair disposed therein;
The at least one electrode has a sealed cylindrical inner space that extends along the axial direction and encloses the heat transfer body, and an electrode front end surface that is perpendicular to the electrode axis .
The wall thickness on the electrode tip side is larger than the wall thickness on the electrode side surface,
The bottom surface of the internal space is flat and parallel to the electrode tip surface;
The discharge lamp characterized in that the internal space has a reduced diameter surface that connects the side surface of the internal space and the bottom surface and has a diameter reduced from the side surface of the internal space toward the bottom surface. The internal space has a curved surface having a predetermined radius of curvature as the reduced diameter surface;
The discharge lamp according to claim 1, wherein the curved surface is formed to satisfy the following conditional expression. However, R represents the radius of curvature of the curved surface, and L1 represents the diameter of the internal space.

0.03 ≦ R / L1 ≦ 0.27
The discharge lamp according to claim 2, wherein the curved surface is formed to satisfy the following expression.

0.06 ≦ R / L1 ≦ 0.20
The internal space has a tapered surface having a predetermined inclination angle as the reduced diameter surface;
The discharge lamp according to claim 1, wherein the tapered surface is formed so as to satisfy the following condition. Here, a represents the inclination angle of the tapered surface with respect to the bottom surface, L1 represents the diameter of the internal space, and L3 represents half the difference between the diameter of the internal space and the diameter of the bottom surface.

0.03 ≦ L3 / L1 ≦ 0.17
10 ≦ a ≦ 60
The electrode has a columnar body part, and a tip part tapering from the body part toward the electrode tip surface,
The discharge lamp according to any one of claims 1 to 4, wherein a bottom surface of the internal space is located in the body portion. A columnar body,
A tip portion that tapers from the body portion toward the electrode tip surface;
A sealed cylindrical interior space that extends along the axial direction and encloses the heat transfer body ;
An electrode tip surface perpendicular to the electrode axis ,
The wall thickness on the electrode tip side is larger than the wall thickness on the electrode side surface,
The bottom surface of the internal space is flat and parallel to the electrode tip surface;
The electrode for a discharge lamp, wherein the internal space has a reduced diameter surface that connects the side surface of the internal space and the bottom surface and has a diameter reduced from the side surface of the internal space toward the bottom surface.

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