discharge lamp

Abstract

To suppress generation of crack in a flow straightening body and the like arranged in a sealed space into which a heat transfer body is encapsulated, in an electrode of a discharge lamp.SOLUTION: In a short-arc type discharge lamp 10, a sealed space is formed in an electrode (an anode) 30, and a heat transfer body M that is molten when the lamp is turned on is encapsulated in the sealed space. A flow straightening body 40 is arranged in the sealed space 50. The flow straightening body 40 has structure with a layered cross section.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to discharge lamps such as short arc discharge lamps, and more particularly to heat dissipation of electrodes. [Background technology]

[0002] During operation of a discharge lamp, the electrode tips become hot, causing electrode materials such as tungsten to melt and evaporate, blackening the discharge tube and reducing the lamp's illuminance. To prevent overheating of the electrodes, including their tips, a known structure is one in which a heat conductor such as a metal is enclosed inside the electrode (see Patent Document 1). In this structure, a heat conductor made of a metal with high thermal conductivity and a relatively low melting point, such as silver, is sealed inside the anode. As the electrode temperature rises during lamp operation, the heat conductor melts and liquefies, generating thermal convection within the enclosed space and preventing overheating of the electrode tips.

[0003] On the other hand, a configuration is known in which a plate-like member that forms a flow path around the electrode axis is placed in the sealed space to promote thermal convection (see Patent Document 2). Also known is a configuration in which a plate-like member that restricts the circumferential flow of the molten heat transfer material is placed in the sealed space to prevent high-temperature creep deformation caused by temperature differences in the sealed space due to thermal convection in the heat transfer material (see Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-006246 [Patent Document 2] Patent No. 6259450 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-28168 Summary of the Invention [Problem to be solved by the invention]

[0005] When the lamp is turned on, convection occurs in the heat transfer material, and the plate-like member placed in the sealed space is subjected to force from the heat transfer material. Furthermore, as the heat transfer material repeatedly solidifies and melts when the lamp is turned off and back on, the temperature drops and rises at different rates depending on the spatial region within the sealed space, resulting in a time difference between solidification and melting. This makes it easy for loads to be applied to specific parts of the plate-like member. Such loads can cause cracks in the plate-like member, potentially resulting in damage.

[0006] Therefore, in the electrode, it is necessary to suppress the occurrence of cracks in the plate-like member disposed in the sealed space that encloses the heat transfer body. [Means for solving the problem]

[0007] A discharge lamp according to one aspect of the present invention comprises a discharge tube and a pair of electrodes arranged opposite each other within the discharge tube, and in at least one of the electrodes, an enclosed space is formed in which a heat transfer material that melts when the lamp is lit is enclosed, and a plate-shaped flow rectifier is arranged within the enclosed space.

[0008] The "flow regulator" here can be configured as a structure, member, etc. that exerts an action, function, etc. related to the flow of the heat transfer material in the sealed space. For example, the flow regulator can be configured in a shape and arrangement that forms a flow path around the electrode axis. Furthermore, the flow regulator can be configured in a shape and arrangement that regulates the flow along at least one of the circumferential direction of the heat transfer material and the electrode axial direction in the sealed space.

[0009] In the present invention, at least a portion of the flow rectifier is formed in a multilayered structure in the thickness direction. That is, it has a structure in which layers are stacked. There are various structures for such a multilayered flow rectifier. For example, the flow rectifier can be configured to have a layered structure (texture, etc.) in its cross section, and a multilayered flow rectifier can be configured by plastic processing. As a plate-shaped flow rectifier with a layered structure, a structure in which layers are formed along boundaries approximately parallel to the plate surface can be formed by, for example, rolling processing.

[0010] On the other hand, it is possible to form a multi-layer flow regulator by stacking multiple thin plate or foil metals. For example, the flow regulator can be configured by stacking metals made of different materials. [Effects of the Invention]

[0011] According to the present invention, it is possible to suppress the occurrence of cracks in the electrodes of a discharge lamp in relation to a flow rectifier or the like that is disposed in a sealed space that encloses a heat transfer body. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a plan view of a discharge lamp according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic cross-sectional view of an anode. [Figure 3] 1 is a schematic cross-sectional view of an example of an anode in a state where the heat transfer body is solidified. [Figure 4] FIG. 2 is a schematic perspective view of a flow regulator. [Figure 5] FIG. 2 is a diagram schematically illustrating a partial cross section of a flow regulator. [Figure 6] FIG. 2 is a diagram showing an optical microscope photograph of a partial cross section of a flow regulator according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] The short arc type discharge lamp 10 is a large discharge lamp capable of outputting high-intensity light, and includes a substantially spherical discharge tube (light emitting tube) 12 made of transparent quartz glass, within which a pair of tungsten electrodes 20, 30 are arranged facing each other (coaxially). On both sides of the discharge tube 12, sealed tubes 13A, 13B made of quartz glass are connected to and integrally formed with the discharge tube 12. Mercury and a rare gas such as halogen or argon gas are sealed in a discharge space DS within the discharge tube 12.

[0014] Electrode 20, which serves as the cathode, is supported by electrode support rod 17A. Sealed in sealed tube 13A are a glass tube (not shown) through which electrode support rod 17A is inserted, lead rod 15A that connects to an external power supply, and metal foil 16A that connects electrode support rod 17A to lead rod 15A. Similarly, for electrode 30, which serves as the anode, are sealed with mounting parts such as a glass tube (not shown) through which electrode support rod 17B is inserted, metal foil 16B, and lead rod 15B. Furthermore, bases 19A and 19B are attached to the ends of sealed tubes 13A and 13B, respectively.

[0015] When a voltage is applied to the pair of electrodes 20, 30, an arc discharge occurs between the electrodes 20, 30, and light is emitted toward the outside of the discharge tube 12. Here, a power of 1 kW or more is input. The light emitted from the discharge tube 12 is guided in a predetermined direction by a reflector (not shown).

[0016] Fig. 2 is a schematic cross-sectional view of the electrode (anode) 30. Fig. 3 is an example of a schematic cross-sectional view of an anode in a state where the heat transfer material is solidified. Fig. 4 is a schematic perspective view of a flow regulator. Note that the electrode (cathode) 20 can also have a similar structure.

[0017] As shown in Figure 2, the anode 30 is composed of a cylindrical body 34 and a truncated cone-shaped tip 32 having an electrode tip surface 30S. The body 34 has a structure in which a sealing lid 60 to which an electrode support rod 17B is attached is joined, and a sealed space 50 is formed within the body 34. Here, the body 34 and the tip 32 are formed from the same metal material, such as tungsten, but they may also be formed from different materials. The sealing lid 60 may also be formed from a different material.

[0018] The sealed space 50 is formed as a cylindrical space here, and is formed coaxially with the electrode axis E. A heat transfer material M is enclosed in the sealed space 50. The heat transfer material M is made of a metal (e.g., silver) with a lower melting point than the body 34 and the sealing lid 60, and melts into a liquid when the lamp is lit, and convects within the sealed space 50. Figure 2 shows the state in which the molten heat transfer material M is convecting.

[0019] A flow straightener 40 is disposed coaxially with the sealed space 50. The flow straightener 40 is configured as a plate-like member that adjusts the flow of the molten heat transfer material M. The flow straightener 40 can be configured with a shape and arrangement that forms a flow path for the heat transfer material M along the electrode axis E, and can also be configured with a shape and arrangement that regulates the flow of the heat transfer material M in a certain direction (for example, a flow along the circumferential direction).

[0020] Here, the flow straightener 40 has a shape that forms a flow path around the electrode axis E. The flow straightener 40 is arranged so as to be a predetermined distance away from the sealed space bottom surface 50B and the sealed space top surface 50T along the direction of the electrode axis E, and so as to be a predetermined distance away from the sealed space side surface 50S in the radial direction. The flow straightener 40 is fixed, for example, by a rod-shaped or plate-shaped fixing member (not shown), or is installed directly in the sealed space 50 without being fixed.

[0021] 4 is an example of a flow rectifier 40 that is composed of curved plates 40A and 40B with a semicircular (C-shaped) cross section and that are arranged facing each other with a gap ST. The curved plates 40A and 40B are symmetrical with respect to the electrode axis E, and the distance between the flow rectifier 40 and the sealed space side surface 50S is approximately equal over the entire circumferential direction. In this example, the flow rectifier 40 is made of a high-melting-point metal (such as tungsten, molybdenum, or tantalum) or an alloy with potassium additive.

[0022] When the lamp is lit, the flow regulator 40 functions as a plate-like member that forms a flow path for the heat transfer body M around the electrode axis E from the opening 41A on the bottom side of the sealed space to the opening 41B on the top side of the sealed space, and heat from the tip of the electrode is transported to the electrode support rod 17B side.

[0023] When the lamp is turned off, the heat transfer material M solidifies, for example, as shown in Figure 3. When the lamp is turned off, the temperature of the heat transfer material M in the internal space of the flow rectifier 40 drops relatively slower than in the external spatial region. Therefore, there is a time difference in the solidification of the heat transfer material M depending on the spatial region, and the heat transfer material M inside the flow rectifier 40 solidifies at a lower liquid level than the heat transfer material M outside the flow rectifier 40, forming a recess of appropriate depth.

[0024] FIG. 5 is a diagram showing a schematic partial cross section of the flow regulator 40. As shown in FIG.

[0025] As shown in Fig. 5, the cross section of the flow straightener 40 forms a multilayered structure along the thickness direction. Such a structure is brought about by the formation of an aggregate structure accompanying plastic deformation. The cross-sectional layered structure of the flow straightener 40 shown in Fig. 5 is brought about by plastic processing, and the crystal grains elongate in the rolling direction to bring about the cross-sectional layered structure. Furthermore, the layers here are approximately parallel to the rolling direction, i.e., along the surface of the flow straightener 40, and the layers are formed here to have approximately the same width (thickness) t, which can be set to fall within the range of several tens of µm to several hundreds of µm.

[0026] The flow rectifier 40, which has such a layered cross-sectional structure, can suppress the progression of cracks even if they occur inside. In other words, the boundaries of the texture stop the progression of the cracks at the boundaries. This prevents damage to the flow rectifier 40, allowing it to perform its function (suppressing electrode temperature) until the end of the lamp's life.

[0027] Such a flow regulator 40 can be manufactured by a manufacturing method involving plastic processing, and the processing temperature, rolling reduction, etc. are determined depending on the raw material and layer thickness. Then, the processed plate material is subjected to a press process such as bending to be curved. For example, hot rolling can be applied, or cold rolling can also be used. Furthermore, the surface can be treated by annealing.

[0028] The above-described flow regulator 40 is made of a single metal material and has a multilayered texture in its cross section. However, it may also be formed into a layered cross section by joining multiple thin plates (foil plates) and then rolling them. By adjusting the joining conditions, it is possible to form gaps on the order of microns between adjacent foil plates (layers). When gaps are formed between adjacent layers, the progression of cracks is effectively stopped.

[0029] On the other hand, it is also possible to prevent substantial gaps from forming between some adjacent layers. Even in this case, since the cracks progress along the grain boundaries (layers), even if peeling of the grain boundaries occurs, the crystal grains themselves will not be destroyed, and damage to the flow straightener 40 can be suppressed. The layered cross section may be formed in only a portion of the flow straightener 40.

[0030] The multilayer cross section may be formed by plastic processing other than rolling (for example, extrusion, drawing, etc.). Alternatively, the multilayer cross section may be formed using a metal 3D printer. In either case, the thickness can be constant or can vary.

[0031] The flow rectifier 40 is not limited to the shape of a curved plate with a semicircular cross section shown in Fig. 4. It may also be configured with two rectangular metal plates arranged facing each other. Even if the flow rectifier 40 is configured with a pair of metal plates each having a flat surface, heat transport along the electrode axis E can be effectively achieved. Furthermore, the flow rectifier 40 may not be configured with a pair of metal plates, but may be configured with three or more metal plates arranged at a predetermined interval from each other.

[0032] The flow regulator 40 may be tapered toward the electrode support rod or may be triangular. Furthermore, the flow regulator 40 may be configured as a tube that forms an internal space. For example, the cross section may be a circular or polygonal (including triangular) tube.

[0033] As described above, the flow regulator 40 can be configured as a plate-like member that regulates the flow of the heat transfer body M in the circumferential direction of the sealed space. For example, the flow regulator can be configured as a single plate, or can be formed as a plate-like member with a cross-shaped or T-shaped cross section.

[0034] In this case, the above-mentioned layered cross section may be formed in at least a part of the flow straightener. Even in such a flow straightener that regulates the flow of a heat transfer body, by having the above-mentioned layered structure, it is possible to suppress the occurrence of cracks and breakage due to the force applied from the heat transfer body.

[0035] The flow rectifier 40 described so far has a configuration having a layered structure in its cross section, but the layered structure is not limited to this. Regardless of whether or not it has a layered structure formed by plastic processing, it may also have a configuration in which plate-shaped materials such as different thin metal plates or foil-shaped metals are combined to form a layered cross section. By stacking plate-shaped members made of such multiple materials, cracks will also progress along the boundaries between adjacent layers, making it possible to suppress damage to the flow rectifier due to cracks.

[0036] For example, a layered flow rectifier can be constructed by sandwiching a thin (foil) molybdenum plate between two thin (foil) tungsten plates. Compared to tungsten, molybdenum is more likely to absorb internal stress through its own elongation, providing a buffering function and preventing damage to the flow rectifier. Alternatively, a material with a higher melting point than the heat transfer body (such as ceramics) can be laminated with a metal plate, or a recrystallized thin (foil) plate can be used. [Example]

[0037] Examples will be described below. The flow rectifier in the examples is a rectangular single plate, and tungsten, which is raw material powder, is pressed to form a shape, sintered, and the sintered body is hot-rolled according to the specified processing temperature, rolling reduction, etc. Here, a partial cross section of the flow rectifier was observed with an optical microscope.

[0038] As shown in Figure 6, in the flow straightener of the example, a texture boundary with a width (thickness) of about 30 μm was formed along the rolling direction (sheet surface direction), and a layered structure was confirmed. Note that some cracks have occurred along the grain boundaries due to the influence of cross-section preparation for cross-sectional observation.

[0039] It should be noted that the flow straightener with a cross-sectional layered shape shown in Fig. 6 is merely one example, and is not limited to the layered shape shown in Fig. 6. By determining the processing temperature and rolling reduction rate in consideration of the thickness of each layer, it is possible to configure a flow straightener with a variety of cross-sectional layered shapes. [Explanation of symbols]

[0040] 10. Discharge lamp 30 Anode (electrode) 40 Flow rectifier 50 Closed space

Claims

1. A discharge tube; a pair of electrodes disposed opposite each other within the discharge tube; At least one of the electrodes has a sealed space formed therein in which a heat transfer material that melts when the lamp is lit is sealed, and a plate-shaped flow rectifier is disposed in the sealed space; A discharge lamp characterized in that at least a part of the flow rectifier is formed in a multi-layered manner in the thickness direction.

2. 2. The discharge lamp according to claim 1, wherein the flow rectifier has a layered structure in its cross section.

3. 3. The discharge lamp of claim 2, wherein the flow rectifier has a texture in which layers are formed along boundaries substantially parallel to the plate surfaces.

4. 4. The discharge lamp according to claim 1, wherein the flow rectifier is configured by laminating a plurality of thin metal plates or foils.

5. 5. The discharge lamp according to claim 4, wherein the flow rectifier is made of a laminate of metals made of different materials.

6. 6. The discharge lamp according to claim 1, wherein the flow rectifier is shaped and arranged to form a flow path around the electrode axis.

7. 6. A discharge lamp according to claim 1, wherein the flow rectifier is shaped and arranged to regulate the flow along at least one of the circumferential direction and the electrode axial direction of the heat transfer body within the sealed space.

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