JP7702070B2 - Discharge lamp and electrodes used in said discharge lamp - Google Patents

Description

The present invention relates to a discharge lamp and an electrode used in the discharge lamp.

Conventionally, exposure devices used in the manufacturing process of semiconductor elements, liquid crystal display elements, or printed circuit boards use discharge lamps as light sources. In these discharge lamps, an anode and a cathode are arranged axially opposite each other inside a light-emitting tube, and a light-emitting substance such as mercury is enclosed inside the light-emitting tube.

In such discharge lamps, the electrodes are subjected to a high thermal load when lit, which can cause the electrode material to evaporate due to overheating of the electrodes. If this evaporated material adheres to the inner wall of the arc tube, the discharge lamp will suffer from what is known as "blackening," causing a problem of reduced light transmittance through the arc tube.

To solve this problem, a discharge lamp has been proposed in which an enclosed space is provided inside the electrode, particularly the anode, and a heat transfer material is enclosed within the enclosed space. The heat transfer material is molten when the lamp is turned on, and convects within the enclosed space due to the temperature distribution across the anode. This convection in the heat transfer material transfers heat from the tip of the anode (the end closest to the cathode) to the rear end (the end furthest from the cathode), lowering the temperature of the anode tip and suppressing the amount of evaporation of the electrode material.

Patent Document 1 and Patent Document 2 describe providing a regulator in an enclosed space to regulate circumferential convection of the heat transfer body. Providing the regulator in the enclosed space prevents holes from being formed in the electrode tip due to circumferential convection of the heat transfer body.

JP 2012-028168 A JP 2017-016761 A

Recently, the market has been demanding higher output and longer life for discharge lamps. Increasing the output of a discharge lamp increases the thermal load on the electrodes, so electrodes that can withstand the increased thermal load for a long period of time are required. The objective of the present invention is to provide a discharge lamp with higher output and longer life, and electrodes for use in said discharge lamp.

The inventors used a radiation thermometer to measure the temperature distribution on the electrode surface when a discharge lamp was turned on in order to investigate the thermal load on the electrodes when the lamp was used at high output. As a result of the measurements, they noticed that there were discharge lamps with high electrode tip temperatures and discharge lamps with large temperature fluctuations on the electrode surface. Temperature fluctuations refer to temperature fluctuations within a short period of time (e.g., one minute). If the electrode tip temperature is high or the electrode surface temperature fluctuation range is large for a long period of time, high-temperature creep deformation will cause holes to form in the electrode tip, leading to leakage of the heat transfer material. This will cause the electrode to lose its ability to dissipate heat, shortening the life of the discharge lamp.

As a result of intensive research by the inventors, which will be described in detail later, it was found that the expansion of the temperature fluctuation range at the electrode tip is caused by turbulence in the convection of the heat transfer body. In order to suppress the turbulence of the heat transfer body, it is advisable to reconsider the design of the regulator provided in the sealed space. In particular, making the regulator larger can effectively suppress the turbulence. However, making the regulator larger increases the volume of the regulator in the sealed space, and the capacity of the heat transfer body decreases. If the capacity of the heat transfer body decreases, the heat transfer efficiency decreases, and the function of the heat transfer body to lower the temperature of the electrode tip is impaired. Therefore, the inventors investigated an optimal design for the regulator that suppresses the turbulence of the heat transfer body while suppressing the increase in the volume of the regulator, and came up with the following discharge lamp.

The present invention provides a discharge lamp having a pair of electrodes disposed opposite to each other in an axial direction, and at least one of the pair of electrodes is
A main body having an enclosed space therein;
a heat transfer body located within the sealed space and having a melting point lower than that of a material constituting the main body;
a regulating body located within the sealed space, having a surface exhibiting a melting point higher than the melting point of the heat transfer body, and regulating convection of the heat transfer body;
The regulator is
A first restricting body having a density greater than that of the heat transfer body;
and a second regulating body having a density lower than that of the heat transfer body.

The convection of the heat transfer body is regulated by a first regulator located near the bottom of the heat transfer body and a second regulator located near the interface of the heat transfer body. By controlling the convection of these regulators, it is possible to suppress turbulence in the heat transfer body. Suppressing turbulence in the heat transfer body reduces the temperature fluctuation range of the electrode inner surface. Furthermore, since the total volume of the regulator divided into the first regulator and the second regulator is smaller than the volume occupied by the regulator when it is not divided, the capacity of the heat transfer body can be secured. Therefore, the heat transfer efficiency is not easily reduced, and the temperature of the electrode tip can be maintained at a low state. As a result, holes in the electrode tip due to high-temperature creep deformation and blackening of the light-emitting tube due to evaporation of the electrode material are suppressed, and the discharge lamp can be made to have a high output and a long life.

The shape of the first control body may be different from the shape of the second control body.

The second regulating body may be rod-shaped and extend in one direction.

The shape of the second regulating body in a cross section perpendicular to the one direction may be circular, triangular, or trapezoidal.

The first and second regulating bodies each have a plurality of blades extending radially outward from a central axis along the axial direction, and the number of blades in the first regulating body may be greater than the number of blades in the second regulating body.

The second regulator may mainly contain titanium or ceramics.

The length of the first regulation body in the axial direction is L1 (mm),
The length of the second regulation body in the axial direction in contact with the heat transfer body is D2 (mm),
When the distance in the axial direction between the first and second regulation bodies is H2 (mm), the following formula (1) may be satisfied.
0 < H2/(L1+D2) ≦ 2...(1)

When the length of the second regulation body in the axial direction that is in contact with the heat transfer body is D2 (mm), the following formula (2) may be satisfied.
D2 ≧ 1.5…(2)

The electrodes used in the discharge lamp of the present invention are
A body having an enclosed space inside the electrode;
a heat transfer material filled in the sealed space and having a melting point lower than that of a material constituting the main body;
a regulating body that is disposed in the sealed space and regulates convection of the heat transfer body and has a surface melting point higher than the melting point of the heat transfer body;
The regulator is
A first regulator having a density greater than that of the heat transfer body;
and a second regulating body having a density lower than that of the heat transfer body.

It is possible to provide a discharge lamp with high output and long life, and electrodes for use in the discharge lamp.

FIG. 1 is a diagram showing an overview of an embodiment of a discharge lamp. FIG. 2 is an enlarged cross-sectional view of the anode in the discharge lamp of FIG. 1 . FIG. 2 is a perspective view showing the inside of a sealed space. 3 is a cross-sectional view taken along the line AA in FIG. 2. 3 is a cross-sectional view taken along the line BB in FIG. 2. FIG. 13 is a diagram showing a state in which a heat transfer body convects in an enclosed space having two restricting bodies. FIG. 13 is a diagram showing a state in which a heat transfer body convects in an enclosed space having one restricting body. 13 is a graph showing the relationship between the heat transfer material occupancy rate and the maximum value of the temperature fluctuation range. FIG. 4 is a top view of a first regulator; FIG. FIG. 4 is a top view of a second regulation body. FIG. 4 is a side view of a second regulation body. FIG. 2 is a cross-sectional view of an anode that has been cooled after heating and melting the heat transfer body. FIG. 4 is a diagram showing cutting positions of an anode. FIG. 13 is a top view of a first modified example of the second restricting body. FIG. 11 is a side view of a first modified example of the second restriction body. FIG. 13 is a top view of a second modified example of the second restricting body. FIG. 13 is a side view of a second modified example of the second restriction body. FIG. 13 is a top view of a third modified example of the second restriction body. FIG. 13 is a side view of a third modified example of the second restriction body. 13 is a first modified example of the first regulator. 13 is a second modified example of the first regulator. 13 is a third modified example of the first regulator.

Embodiments of a discharge lamp will be described with reference to the drawings. Note that the following drawings, excluding the graphs, are schematic illustrations, and the dimensional ratios in the drawings do not necessarily match the actual dimensional ratios, and the dimensional ratios between the drawings do not necessarily match.

In the following, each drawing except for graphs will be described with reference to the XYZ coordinate system. In this specification, when a direction is expressed and a positive or negative direction is to be distinguished, it is described with a positive or negative sign, such as "+X direction" and "-X direction". When a direction is to be expressed without distinguishing between positive and negative directions, it is simply described as "X direction". In other words, in this specification, when it is simply described as "X direction", both the "+X direction" and the "-X direction" are included. The same applies to the Y direction and the Z direction. In the embodiment described below, the -Z direction represents the direction of gravity.

[Discharge Lamp Overview]
An outline of one embodiment of a discharge lamp will be described with reference to Fig. 1. The discharge lamp 100 is a short arc type discharge lamp including an arc tube 1, an anode 2 and a cathode 3 disposed opposite each other in the extension direction of a central axis Z1 inside the arc tube 1, and lead rods 4 supporting the anode 2 and the cathode 3, respectively. In this embodiment, the discharge lamp 100 is disposed so that the anode 2 is located above the cathode 3 (in the +Z direction), and the discharge lamp 100 is turned on.

A short arc type discharge lamp is one in which the tip of the anode 2 and the tip of the cathode 3 are spaced apart by a distance of 40 mm or less (the value at room temperature when there is no thermal expansion). An example of such a discharge lamp is a discharge lamp with a rated power of 2 kW to 35 kW, which is used in exposure devices used in the manufacturing process of semiconductor elements, liquid crystal display elements, printed circuit boards, etc. In the discharge lamp 100 of this embodiment, the tip of the anode 2 and the tip of the cathode 3 are spaced apart by a distance of 6 mm.

The light-emitting tube 1, anode 2, cathode 3, and lead rod 4 are all arranged so as to be centered on the central axis Z1. The anode 2 is arranged above the cathode 3 (in the +Z direction). Sealing tubes 11 are provided on both ends of the light-emitting tube 1 in the extension direction of the central axis Z1. The sealing tubes 11 are fitted with bases 12 that are electrically connected to the lead rods 4.

The light emitting tube 1 is formed from a glass tube. The light emitting tube 1 has a region where the inner diameter of the glass tube increases from both ends of the central axis Z1 toward the center. This region where the inner diameter increases may have a spherical or ellipsoidal shape. The glass tube may be made of, for example, quartz glass. The region where the inner diameter increases functions as a light emitting space. A light emitting substance such as mercury is enclosed in the light emitting space.

[Anode Overview]
The outline of the anode 2 will be described with reference to FIG. 2. FIG. 2 is an enlarged cross-sectional view of the anode 2 in the discharge lamp of FIG. 1. The anode 2 has a shape of a body of revolution centered on a central axis Z1. FIG. 2 shows a cross section of the anode 2 in a plane passing through the central axis Z1. In FIG. 2, a tip 13 of the anode 2 close to the opposing cathode 3 is shown on the lower side (−Z side), and a rear end 14 to which a lead rod 4 (not shown in FIG. 2) is connected is shown on the upper side (+Z side). Note that the regulating bodies (10, 20) shown in FIG. 2 are shown by their side shapes, not their cross-sectional shapes.

The anode 2 has a body 5 of the anode 2, a heat transfer body 9, and a regulator (10, 20) that regulates convection in the heat transfer body 9. The body 5 includes a container 5a and a lid 5b. The lid 5b is attached so that it cannot be removed from the container 5a. When the lid 5b is attached to the container 5a, an enclosed space 6 is formed inside the body 5. The body 5 is made of a high-melting point material so that the body 5 is unlikely to melt when the discharge lamp 100 is turned on. In this embodiment, the body 5 (container 5a and lid 5b) is made of a material that mainly contains tungsten.

In this embodiment, the sealed space 6 includes a gas space 8 in addition to the heat transfer body 9 and the regulating body (10, 20). The gas space 8 is filled with, for example, air or an inert gas (for example, argon). The central axis of the sealed space 6 in this embodiment is the same as the central axis Z1 of the anode 2. The shape of the inner wall 15 of the sealed space 6 in the anode 2 in this embodiment is a shape composed of a truncated cone arranged so that the bottom surface is small and the top surface is large, and a cylinder arranged in contact with the truncated cone.

The heat conductor 9 exists as a liquid when the discharge lamp 100 is turned on and at a high temperature. The heat conductor 9 exists as a solid when the discharge lamp 100 is turned off. Therefore, the melting point of the heat conductor 9 is lower than the melting point of the material that constitutes the body 5. When the discharge lamp 100 is turned on and the heat conductor 9 melts, the heat conductor 9 convects in the sealed space 6 and transfers heat near the tip 13 of the anode 2 to the rear end 14 of the anode 2. The heat transferred to the rear end 14 is transferred to the lead rod 4 (not shown in FIG. 2) and is released from the electrode surface to the outside of the electrode by radiation. This reduces the temperature of the tip 13 of the anode 2.

The material constituting the heat transfer body 9 is composed of a thermally conductive material. The material constituting the heat transfer body 9 is preferably a material having a higher thermal conductivity than the material constituting the main body 5. In this embodiment, a material containing mainly silver is used as the material constituting the heat transfer body 9. A material containing mainly gold may also be used as the material constituting the heat transfer body 9.

[Overview of the Regulatory Body]
The outline of the regulating body (10, 20) will be described with reference to Fig. 3, Fig. 4A, and Fig. 4B in addition to Fig. 2. Fig. 3 is a perspective view showing the inside of the sealed space 6. In Fig. 3, only the regulating body (10, 20) is drawn in solid lines. Fig. 4A is a cross-sectional view taken along line A-A in Fig. 2. Fig. 4B is a cross-sectional view taken along line B-B in Fig. 2. In Figs. 4A and 4B, only the main body 5 is shown hatched with oblique lines.

As shown in Figures 2 and 3, in this embodiment, the regulating body (10, 20) is composed of a first regulating body 10 and a second regulating body 20. The first regulating body 10 and the second regulating body 20 are arranged side by side along the Z direction.

The density of the first regulator 10 is greater than that of the heat conductor 9. The density of the second regulator 20 is less than that of the heat conductor 9. Therefore, when the heat conductor 9 melts due to lighting of the discharge lamp 100, the first regulator 10 sinks into the heat conductor 9 and the second regulator 20 floats on the heat conductor 9. Therefore, the second regulator 20 is located in the +Z direction of the first regulator 10.

As shown in FIG. 4A, the central axis of the first control body 10 is indicated as Z2. The central axis Z2 extends in a direction along the Z direction (axial direction). It is preferable that the central axis Z2 overlaps with the central axis of the sealed space 6. However, the first control body 10 may be pushed by the convection of the heat transfer body 9 and tilted, so that the central axis Z2 may not overlap with the central axis of the sealed space 6.

In this embodiment, the first regulating body 10 has four blades 10b. Each blade 10b extends radially outward from a central axis Z2 along the Z direction. In Figures 2, 3, and 4A, two of the four blades 10b are shown extending in the ±X direction from the central axis Z2. The remaining two of the four blades 10b are shown extending in the ±Y direction from the central axis Z2. When the first regulating body 10 is viewed from the +Z direction, the first regulating body 10 is cross-shaped. There is usually a gap G1 between most of the outer surface of the first regulating body 10 and the inner wall 15 that constitutes the sealed space 6 (see Figure 4A).

In this embodiment, the second regulator 20 is rod-shaped and long in one direction (Y direction in FIG. 4B). When the heat transfer body 9 is melted, the longitudinal direction of the second regulator 20 is along the interface 9s between the gas space 8 and the heat transfer body 9. The portion of the second regulator 20 above the interface 9s contacts the gas space 8. The portion of the second regulator 20 below the interface 9s contacts the heat transfer body 9. There is usually a gap G2 between the longitudinally opposing ends (E1, E2) of the second regulator 20 and the inner wall 15 that constitutes the sealed space 6 (see FIG. 4B).

[Actions of two regulatory bodies]
The action of the two regulators (10, 20) will be described with reference to Figures 5A and 5B. Figures 5A and 5B are perspective views showing the inside of the sealed space 6, respectively, and show simplified results of a convection simulation of the heat transfer body 9. Figure 5A includes two regulators (10, 20) each having the above-mentioned shape. Figure 5B includes only the regulator 30 having the shape of the first regulator 10 described above. When the discharge lamp 100 is turned on, the heat transfer body 9 melts and starts convection. The arrows shown in the sealed space 6 in Figures 5A and 5B indicate the direction of convection of the heat transfer body 9.

Now, let us consider FIG. 5B. The regulator 30 is submerged in the molten heat transfer body 9. The interface 9s between the heat transfer body 9 and the gas space 8 is far from the upper surface of the regulator 30, and a large amount of the heat transfer body 9 is present on the regulator 30. In FIG. 5B, the two flows of the heat transfer body 9 regulated by the regulator 30 are indicated by arrows labeled "fb". The heat transfer body 9 regulated by the regulator 30 forms a flow that rises toward the interface 9s. When the flow of the heat transfer body 9 reaches the vicinity of the interface 9s, it spreads radially outward along the interface 9s. At this time, a region cf is generated where the two flows fb of the heat transfer body 9 collide with each other. In the region cf, turbulence occurs due to the collision of the two flows fb. When turbulence occurs, the transfer of heat by the heat transfer body 9 becomes unstable, and the temperature fluctuation range of the anode 2 increases.

Now, let us consider FIG. 5A. In FIG. 5A, the two flows of the heat transfer body 9 regulated by the first regulator 10 are indicated by arrows labeled "fa." The heat transfer body 9 regulated by the first regulator 10 forms a flow that rises toward the interface 9s. When the flow of the heat transfer body 9 reaches the vicinity of the interface 9s, it spreads radially outward along the interface 9s. However, since the second regulator 20 exists between the two flows fb of the heat transfer body 9, the two flows fb are unlikely to collide with each other. Therefore, the generation of turbulence in the region cf as shown in FIG. 5B is suppressed.

The conditions used in the above convection simulation are as follows:
<Discharge Lamp 100>
It has the shape shown in FIG.
Material of light emitting tube 1: quartz glass Distance between anode 2 and cathode 3: 6 mm
Filling in the light emitting tube 1: mercury 2.0 mg/cc, argon 100 kPa
Rated current: 200A
Rated power: 12kW
<Electrode Overview>
The anode 2 has an enclosed space 6 therein.
It has the shape shown in FIG.
Volume of the enclosed space 6: 17 ^cm3
Material of heat transfer body 9: silver Filling gas in gas space 8: argon 100 kPa
Material of the main body 5: Material mainly containing tungsten <First regulator 10 and regulator 30>
Regulator material: material mainly containing tungsten <second regulator 20>
Materials of the regulated body: Mainly materials containing titanium

Figure 6 is a graph showing the relationship between the heat transfer body occupancy rate relative to the regulating body (10, 20) and the maximum temperature fluctuation range TX. This graph was obtained by performing a convection simulation of the heat transfer body 9. The conditions for the convection simulation are the same as those described above.

The heat transfer material occupancy rate will now be described. First, the following parameters are set as shown in FIG.
Length of first regulation body 10 in Z direction: L1 (mm)
Distance from the bottom surface of the second restriction body 20 to the interface 9s: D2 (mm)
Distance from the upper surface of the first restricting body 10 to the lower surface of the second restricting body 20: H2 (mm)

The sum of the length L1 and the distance D2 means the total length of the first regulator 10 and the second regulator 20 in the Z direction in the heat transfer body. The distance H2 means the length in the heat transfer body in the Z direction where the regulators (10, 20) are not present. The ratio of these lengths, i.e., H2/(L1+D2), can be considered as the ratio of the area in the Z direction where the regulators are present to the area where the heat transfer body is present. The ratio of the area in the Z direction where the regulators are present to the area where the heat transfer body is present simply approximates the heat transfer body occupancy rate for the regulators (10, 20). Therefore, in this specification, the value calculated from H2/(L1+D2) is defined as the heat transfer body occupancy rate for the regulators (10, 20).

The maximum value TX of the temperature fluctuation range will be explained. The temperature fluctuation range is expressed as the difference between the maximum temperature and the minimum temperature at any location on the inner surface of the electrode (the inner wall 15 of the sealed space 6) during a specified time (for example, one minute) when the discharge lamp is turned on. If the state in which the temperature fluctuation range is large continues for a long time, high-temperature creep deformation causes a concave deformation of the inner surface of the electrode near the tip of the electrode, causing a hole in the tip of the electrode and leakage of the heat conductor 9. As a result, the electrode loses its heat dissipation ability, the electrode becomes overheated, and the deterioration of the discharge lamp progresses rapidly. The temperature fluctuation range shows different values depending on the location of the inner surface of the electrode. Note that when actually measuring the temperature fluctuation range, it is difficult to directly measure the temperature of the inner surface of the electrode, so as an alternative, it is better to estimate the temperature of the inner surface of the electrode by measuring the outer surface of the electrode with a radiation thermometer or the like.

The maximum value TX of the temperature fluctuation range (unit: °C, hereinafter sometimes referred to as "maximum value TX") indicates the maximum value of the temperature fluctuation range that differs depending on the location on the inner surface of the electrode. By suppressing the maximum value TX, the thermal load on the anode 2 can be reduced, and damage such as holes in the tip of the electrode due to high-temperature creep deformation can be suppressed. The smaller the maximum value TX, the better. As a guideline, it is preferable for the maximum value TX to be 13°C or less.

Figure 6 shows the relationship between the heat transfer material occupancy rate, approximated by H2/(L1+D2), and the maximum value TX. The points plotted with triangular marks are from a reference configuration (see Figure 5B) in which there is a regulating body 30 corresponding to the first regulating body 10, and there is no second regulating body 20. Curve C1 is an approximation curve of the points plotted with triangular marks. The points plotted with circular marks are from this embodiment (see Figure 5A) in which two regulating bodies (10, 20) are provided. Curve C2 is an approximation curve of the points plotted with circular marks. In the reference configuration in which there is no second regulating body 20, the distance D2 is 0 (mm), so the value approximating the heat transfer material occupancy rate is essentially H2/(L1+0), i.e., H2/L1.

From FIG. 6, even when the heat transfer body occupancy rate is the same, the maximum value TX of the embodiment (curve C2) is smaller than the maximum value TX of the reference embodiment (curve C1). This shows that even if there is no change in the capacity of the heat transfer body 9, the maximum value TX can be reduced by changing one regulator to two regulators.

As described above, it is preferable that the maximum value TX is equal to or less than 13° C. From Fig. 6, when the maximum value TX of the C2 curve is equal to or less than 13° C., H2/(L1+D2) satisfies formula (1).

0 < H2/(L1+D2) ≦ 2...(1)

Conversely, when formula (1) is satisfied, the maximum value TX of the temperature fluctuation range is 13° C. or less. Note that formula (1) is based on the above simulation conditions and the shape of the regulating body (10, 20), but formula (1) holds even if other simulation conditions and a different shape of the regulating body (10, 20) are used.

The distance D2 from the bottom surface of the second regulating body 20 to the interface 9s can be rephrased as the sinking depth of the second regulating body 20. The inventors considered that the convection regulating effect of the second regulating body 20 would be affected if the distance D2 becomes smaller (i.e., if the sinking depth of the second regulating body 20 becomes shallower). Therefore, a convection simulation was performed to change the value of the distance D2 and determine the maximum value TX of the temperature fluctuation range for each case.

The results of the convection simulation are shown in Table 1 below. Note that the heat transfer material occupancy rate was set to H2/(L1+D2)=2.0.

From Table 1, it was found that in order to keep the maximum temperature fluctuation range TX at 13°C or less, the distance D2 from the bottom surface of the second regulating body 20 to the interface 9s, i.e., the subsidence depth, should be set to 1.5 mm or more. The distance D2 can be adjusted by designing the shape, size (volume) or density (material, etc.) of the second regulating body 20.

Now, let us look at the amount of the heat transfer body 9. In FIG. 5A, the amount of the heat transfer body 9 is reduced by the volume of the second regulator 20 immersed in the heat transfer body 9 compared to FIG. 5B. When the amount of the heat transfer body 9 is reduced, the heat transfer efficiency by the heat transfer body 9 is reduced. However, as a result of the above simulation, the average temperature of the anode tip in FIG. 5B was 3060°C, whereas the average temperature of the anode tip in FIG. 5A was 3063°C. In other words, it was found that the temperature reduction at the anode tip by placing the second regulator 20 was only 3°C, and the reduction in heat transfer efficiency due to the reduction in the amount of the heat transfer body 9 was limited. From this, it was found that the advantage of lowering the maximum value TX by placing the second regulator 20 shown in FIG. 6 is greater than the disadvantage of the reduction in heat transfer efficiency due to the reduction in the amount of the heat transfer body 9.

[Regulatory body details]
The dimensions and shapes of the regulating bodies (10, 20) will be described in detail with reference to Figures 7A, 7B, 8A, and 8B. Figure 7A is a top view of the first regulating body 10, and the first regulating body 10 is viewed in the -Z direction. Figure 7B is a side view of the first regulating body 10, and the first regulating body 10 is viewed in the +X direction. Figure 8A is a top view of the second regulating body 20, and the second regulating body 20 is viewed in the -Z direction. Figure 8B is a side view of the second regulating body 20, and the second regulating body 20 is viewed in the +Y direction.

The four blades 10b constituting the first regulating body 10 are designed to withstand the impact of the convective heat transfer body 9 or the stress due to the thermal expansion of the heat transfer body 9. For example, the thickness T1 of the blade 10b (see FIG. 7A) may be, for example, 2 mm or more, and preferably 3 mm or more. The height (length in the Z direction) L1 of the blade 10b (see FIG. 7B) may be 3 mm or more, and preferably 6 mm or more. The radial length B1 of the blade 10b may be 40% or more, and preferably 45% or more, of the inner diameter D6 of the sealed space 6 (see FIG. 3). The length B2 in the X or Y direction of the regulating body (see FIG. 7B) may be 80% or more, and preferably 90% or more of the inner diameter D6 of the sealed space 6 (see FIG. 3). The length B1 and the length B2 are preferably smaller than the inner diameter D6 of the sealed space 6 (see FIG. 3) to the extent that the gap G1 can be provided.

In this embodiment, the second regulator 20 is rod-shaped and long in the Y direction (see FIG. 8A). The length B3 of the second regulator 20 in the Y direction may be, for example, 80% or more of the inner diameter D6 (see FIG. 3) of the sealed space 6, and preferably 90% or more. The central axis of the second regulator 20 in the Z direction is at the position Z3. The width of the second regulator 20 is not uniform, and the width W1 at the end E1 in the +Y direction is larger than the width W2 at the end E2 in the -Y direction. The width gradually decreases from the end E1 to the end E2. Since the second regulator is rod-shaped such that the width gradually decreases from one end E1 to the other end E2, the convection of the heat transfer body 9 is stabilized. The width W1 is preferably 3 mm or more and 6 mm or less.

There is a risk that the second regulator 20 will rotate around the Y direction, which is the longitudinal direction, and tip over. When the second regulator 20 tips over, it generates turbulence in the heat transfer body 9. Reducing the risk of the second regulator 20 tipping over leads to suppressing the generation of turbulence. The second regulator 20 has an isosceles trapezoidal shape in a cross section parallel to the XZ plane perpendicular to the longitudinal direction (Y direction) (see FIG. 8B). In this cross section, the width of the upper base V1 of the second regulator 20 in the X direction is smaller than the width of the lower base V2 in the X direction. This causes the center of gravity of the second regulator 20 to shift toward the lower base V2, reducing the risk of the second regulator 20 tipping over in the molten heat transfer body 9. The angle θ1 is preferably 30 degrees or more and 60 degrees or less. The length (height) L2 of the second regulator 20 in the Z direction is preferably 3 mm or more, and preferably 6 mm or more. The second control body 20 may have a triangular shape in a cross section parallel to the XZ plane.

In the above simulation, the first regulator 10 is made of a material that mainly contains tungsten, and the second regulator 20 is made of a material that mainly contains titanium, but this combination of materials is not limited. Ceramics such as aluminum oxide and magnesium oxide may also be used as the material for the second regulator 20.

In order to prevent the regulator (10, 20) from melting when the discharge lamp 100 is turned on, it is preferable that the melting point of the material constituting the regulator (10, 20) is higher than the melting point of the material constituting the heat conductor 9. In addition, in order to prevent the regulator (10, 20) from reacting with the material constituting the main body 5 or the material constituting the heat conductor 9 and changing in quality, it is preferable that the material constituting the regulator (10, 20) is a material that has a sufficiently low reactivity with the material constituting the main body 5 and the material constituting the heat conductor 9. However, the base material of the second regulator 20 may be made of a material that can react with the material constituting the main body 5 or the material constituting the heat conductor 9 (e.g., chromium or zirconium when the heat conductor 9 is silver), and the base material may be surrounded by a material (e.g., titanium) that has a sufficiently low reactivity with the material constituting the main body 5 and the material constituting the heat conductor 9. The method of forming the titanium or the like around the base material may be, for example, a deposition method or various plating methods.

Regarding the manufacturing method of the first regulating body 10, four blades 10b may be arranged at 90 degree intervals around the Z2 axis and joined together. The first regulating body 10 may be formed by joining a flat plate extending in the X direction and a flat plate extending in the Y direction, crossing them on the Z1 axis. The first regulating body 10 may be manufactured by integral molding. Note that even if two blades 10b extending in a straight line are made up of a single flat plate, the single flat plate is counted as being made up of two different blades extending radially outward from the center. The same applies to the other examples of regulating bodies.

[Method for determining dimensions of each component from manufactured anode]
A method for determining the dimensions of each member or each part from the manufactured anode 2 will be described. The method described below is particularly suitable for determining the dimensional design values of the anode 2 in a discharge lamp that has been turned on for use or testing after the manufacture of the discharge lamp. This is because the interface 9s of the anode 2 used for lighting is not formed flat, and it is difficult to determine the position of the interface 9s in the Z direction. The position of the interface 9s in the Z direction is used to calculate the distance D2 from the bottom surface of the second regulator 20 to the interface 9s.

The main reason why the interface 9s of the anode 2 that has been used once for lighting is not formed flat is explained. Figure 9 is a cross-sectional view of the anode 2 that has been cooled after the heat transfer body 9 has been heated and melted. In Figure 9, the second regulator 20 is shown by a broken line to make it easier to read the shape of the interface 9s. After the discharge lamp 100 is manufactured, the heat transfer body 9 of the anode 2 of the discharge lamp 100 that has been turned on for use or testing has been heated and melted at least once. When the anode 2 is cooled when the lamp is turned off, the temperature decreases from the surface of the anode 2 toward the inside of the anode 2. As a result, the timing of thermal contraction associated with solidification differs between the surface of the anode 2 and the inside of the anode 2, so that the interface 9s between the heat transfer body 9 and the gas space 8 may be recessed near the central axis Z1, as shown in Figure 9.

The dimensional design values are obtained from the manufactured anode 2 according to the following procedure.
(Step 1) The anode 2 is removed from the discharge lamp 100, and the outer diameter D1 of the anode 2 is measured. The container 5a is cut along the XY plane at a position (line segment P-P in FIG. 10) that crosses the gas space 8 (a portion that does not include the heat conductor 9) relatively above the sealed space 6. By cutting, the anode 2 is divided into a first electrode portion p1 including the heat conductor 9 and the regulating body (10, 20) and a second electrode portion p2 including the lid 5b (see FIG. 10).

(Step 2) Measure the weight a of the first electrode portion p1. Also, take a small amount of heat transfer body 9 from the cut surface to analyze the components and estimate the density ρ. For example, a fluorescent X-ray device or the like may be used to analyze the components.

(Step 3) The first electrode portion p1 is immersed in a liquid that does not dissolve the anode 2 but dissolves the heat transfer body 9, and the heat transfer body 9 is dissolved and the regulator (10, 20) is removed from the first electrode portion p1. For example, nitric acid is used as such a liquid. Nitric acid dissolves silver used as the heat transfer body 9 and does not easily dissolve the main body 5 of the anode 2 and the regulator (10, 20). Then, the weight b including the regulator (10, 20) is measured from the first electrode portion p1 excluding the heat transfer body 9. The volume VM of the heat transfer body 9 is calculated by the formula (3).
VM = (a-b)/ρ...(3)

(Step 4) Measure the length L2 of the second regulator in the Z direction. Also, float the second regulator 20 on a molten metal with a density close to that of the heat transfer body 9, and measure the sinking depth, that is, the distance D2 from the bottom surface of the second regulator 20 to the interface 9s.

(Step 5) A liquid (e.g., water) having a volume equal to the volume VM of the heat transfer body 9 obtained in step 3 is poured into the sealed space 6 of the anode 2, and the regulators (10, 20) are submerged in the liquid. Then, a distance H3 from the top of the first regulator 10 to the liquid surface is measured. A distance H2 between the first regulator 10 and the second regulator 20 in the Z direction is obtained using equation (4).
H2 = H3-L2...(4)

[Modification of the second regulator]
11A and 11B are a first modified example of the second regulator 25. FIG. 11A is a top view of the second regulator 25, looking at the second regulator 25 in the -Z direction. FIG. 11B is a side view of the second regulator 25, looking at the second regulator 25 in the +Y direction. The second regulator 25 is rod-shaped long in the Y direction, and has a shape in which the bottom surfaces of two truncated cones are in contact with each other. Position C5 in the longitudinal direction (Y direction) passes through the central axis Z3 extending in the Z direction. The diameter W3 at position C5 is larger than the diameter W4 at the end positions (E1, E2) in the longitudinal direction. The diameter gradually decreases from position C5 to position E1 (or E2). When the orientation of the second regulator 25 does not coincide with the direction of convection of the heat transfer body 9, the second regulator 25 can be rotated slightly around the central axis Z3 to coincide with the direction of convection of the heat transfer body 9. In addition, since the diameter gradually decreases toward the outside in the radial direction, the convection of the heat transfer body 9 is stabilized. In addition, in the case where the side surface or cross section is circular like the second restricting body 25, the second restricting body 25 does not fall over, and therefore does not cause turbulence due to the second restricting body 25 falling over. In addition, it is easy to process into the shape of this modified example, and the processing cost is low.

12A and 12B are a second modified example of the second regulator 26. FIG. 12A is a top view of the second regulator 26, looking at the second regulator 26 in the -Z direction. FIG. 12B is a side view of the second regulator 26, looking at the second regulator 26 in the +Y direction. The second regulator 26 is rod-shaped long in the Y direction, and has a truncated cone shape with circular ends E1 and E2. The diameter of the second regulator 20 is not uniform, and the diameter W1 at the end E1 in the +Y direction is larger than the diameter W2 at the end E2 in the -Y direction. The diameter gradually decreases from the end E1 to the end E2. Since the second regulator is rod-shaped with a gradually decreasing width from one end E1 to the other end E2, the convection of the heat transfer body 9 is stabilized. In addition, it is easy to process into the shape of this modified example, and the processing cost is low.

Figures 13A and 13B are a third modified example of the second regulating body. Figure 13A is a top view of the second regulating body 27, looking at the second regulating body 27 in the -Z direction. Figure 13B is a cross-sectional view of the second regulating body 27 at the line segment F-F, looking at the second regulating body 27 in the -Y direction. As shown in Figure 13A, the second regulating body 27 is Y-shaped. As shown in Figure 13B, the cross section of the second regulating body 27 at the line segment F-F is a rectangle with the Z direction as the longitudinal direction. All three blades (27a, 27b) of the second regulating body 27 are tangent to a tangent line C6 extending in the Z direction. The tangent line C6 is located at a position shifted from the central axis Z3 of the Y-direction length and the X-direction length. Therefore, of the three blades (27a, 27b), one blade 27b is longer than the other two blades 27a. Convection of the heat transfer body 9 is easily formed along one long blade 27b, so it is easy to stabilize. In addition, because the second regulator 27 has a Y-shape, once the second regulator 27 is aligned with the direction of convection in the heat transfer body 9, the position of the second regulator 27 is less likely to change because factors that could cause turbulence, such as the second regulator 27 tipping over, are small, making it easier to stabilize the convection.

Although not illustrated or described, as a fourth modified example, the second regulator 20 may have a cross shape like the first regulator 10. The convection of the heat transfer body 9 is more likely to be stable if the number of blades of the second regulator 20 is smaller than the number of blades of the first regulator 10.

Figure 14 is a first modified example of the first regulator. Figure 14 is a top view of the first regulator 17, looking at the first regulator 17 in the -Z direction. As shown in Figure 14, the first regulator 17 has a T-shape. The three blades (17a, 17b) of the first regulator 17 are all tangent to a tangent C6 extending in the Z direction. The tangent C6 may be offset from the central axis Z3 or may overlap with the central axis Z3. The T-shaped first regulator 17 has fewer blades than the cross-shaped first regulator 10, so the volume of the regulator is smaller and the amount of heat transfer body 9 can be increased. Note that the first regulator 17 has two blades 17a arranged in a straight line, so the two blades 17a may be composed of a single plate.

Figure 15 shows a second modified example of the first regulator 18. Figure 15 is a top view of the first regulator 18, looking at the first regulator 18 in the -Z direction. The first regulator 18 has three blades 18b. All three blades are tangent to a tangent line C6 extending in the Z direction. The tangent line C6 overlaps with the central axis Z3. The first regulator 18 has fewer blades than the cross-shaped first regulator 10, so the volume of the regulator is smaller and the amount of heat transfer body 9 can be increased. In addition, the blades 18b are at equal angles (120°) to each other, so the first regulator 18 is less likely to tilt and is easier to maintain a stable posture. The stability of the first regulator 18 leads to the stabilization of convection.

Figure 16 shows a third modified example of the first regulating body. Figure 16 is a side view of the first regulating body 19, looking at the first regulating body 19 in the +X direction. The first regulating body 19 has four blades 19a. The outer surface 19t of each blade 19a has a tapered shape. Therefore, the radial length of the upper surface (surface on the +Z side) of the blade 19a is smaller than the radial length of the lower surface (surface on the -Z side).

The above describes the embodiment and its modified examples. The present invention is not limited to the above-described embodiment and its modified examples, and various improvements or modifications can be made to the above-described embodiment and its modified examples, or the modified examples can be combined, without departing from the spirit of the present invention.

In the above, the regulating body is composed of a first regulating body 10 and a second regulating body 20, but it may be composed of three or more regulating bodies.

In the above, an example was described in which the anode 2 has a body 5 having an enclosed space 6, a regulator (10, 20) in the enclosed space 6, and a heat transfer body 9 in the enclosed space 6. The cathode 3 may have a body having an enclosed space, and multiple regulators and heat transfer bodies in the enclosed space. The discharge lamp 100 may be arranged so that the cathode 3 is located above the anode 2.

1: Arc tube 2: Anode 3: Cathode 4: Lead rod 5: Main body 5a: Container 5b: Lid 6: Sealed space 8: Gas space 9: Heat transfer body 9s: Interface (between heat transfer body and gas space) 10, 17, 18, 19: First regulator 10b, 17a, 17b, 18b, 19a: Blade (of first regulator) 11: Sealing tube 12: Base 13: Tip (of electrode) 14: Rear end (of electrode) 15: Inner wall 19t (of main body): Outer surface (of blade) 20, 25, 26, 27: Second regulator 27a, 27b: Blade (of second regulator) 30: First regulator 100 (when no second regulator is present): Discharge lamp

Claims (9)

In a discharge lamp having a pair of electrodes arranged opposite to each other in an axial direction, at least one of the pair of electrodes is
A main body having an enclosed space therein;
a heat transfer body located within the sealed space and having a melting point lower than that of a material constituting the main body;
a regulating body located within the sealed space, having a surface exhibiting a melting point higher than the melting point of the heat transfer body, and regulating convection of the heat transfer body;
The regulator is
A first restricting body having a density greater than that of the heat transfer body;
and a second regulator having a density lower than that of the heat conductor. The discharge lamp of claim 1, characterized in that the shape of the first regulator is different from the shape of the second regulator. The discharge lamp according to claim 2, characterized in that the second regulator is rod-shaped and extends in one direction. The discharge lamp according to claim 3, characterized in that the shape of the second regulator in a cross section perpendicular to the one direction is circular, triangular or trapezoidal. The discharge lamp according to claim 2, characterized in that the first and second regulators each have a plurality of blades extending radially outward from a central axis along the axial direction, and the number of the blades of the first regulator is greater than the number of the blades of the second regulator. The discharge lamp according to any one of claims 1 to 5, characterized in that the second regulator mainly contains titanium or ceramics. The length of the first regulation body in the axial direction is L1 (mm),
The length of the second regulation body in the axial direction in contact with the heat transfer body is D2 (mm),
When the distance between the first and second regulation bodies in the axial direction is H2 (mm), the following formula (1) is satisfied: 0 < H2/(L1+D2) ≦ 2 (1)
6. A discharge lamp according to claim 1, characterized in that: When the length of the second regulator in the axial direction in contact with the heat transfer body is D2 (mm), the following formula (2) is satisfied: D2 ≧ 1.5 (2)
6. A discharge lamp according to claim 1, characterized in that: An electrode for use in a discharge lamp, the electrode comprising:
A main body having an enclosed space therein;
a heat transfer body located within the sealed space and having a melting point lower than that of a material constituting the main body;
a regulating body that is located within the sealed space, has a surface that exhibits a melting point higher than the melting point of the heat transfer body, and regulates convection of the heat transfer body;
The regulator is
A first restricting body having a density greater than that of the heat transfer body;
and a second regulator having a density lower than that of the heat transfer body.