discharge lamp

Abstract

To suppress the occurrence of cracks in a flow regulator arranged in a closed space that encloses a heat transfer body in an electrode of a discharge lamp.SOLUTION: A closed space 50 is formed in an anode 30 of a discharge lamp 10, and a heat transfer body M that melts when a lamp is lit is enclosed therein. Further, a flow regulator 40 in which first and second plate-like members 40A and 40B are stacked is arranged in the closed space 50. The thicknesses T1 and T2 of the first and second plate-like members 40A and 40B are different, and the first plate-like member 40A is made thicker than the second plate-like member 40B.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 tip becomes 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 electrode, including the electrode tip, a structure in which a heat conductor such as a metal is enclosed within the electrode is known (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 within the anode. As the electrode temperature rises during lamp operation, the heat conductor melts and liquefies. This causes thermal convection within the enclosed space, transporting heat from the electrode tip to the electrode support rod on the opposite side.

[0003] Also known are configurations in which a plate-shaped member (flow regulator) that forms a flow path along the electrode axis is placed within the sealed space to promote thermal convection (see Patent Document 2), and configurations in which a plate-shaped member (regulator) that restricts the circumferential flow of the molten heat transfer material is placed within the sealed space to prevent high-temperature creep deformation caused by temperature differences within the sealed space due to thermal convection of the heat transfer material is placed within the sealed space (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. 2012-028168 Summary of the Invention [Problem to be solved by the invention]

[0005] When the lamp is turned on, the flow of molten heat transfer material acts on the flow rectifier, etc., causing it to tilt in some cases. When the flow rectifier, etc. tilts, there is a temperature difference between the bottom and ceiling sides of the sealed space, so the amount of thermal expansion of the flow rectifier, etc. varies along the electrode axis. This causes deformation such as warping, which can lead to cracks and damage to the flow rectifier, etc.

[0006] Therefore, in the electrode, it is required to suppress the occurrence of cracks in the flow regulator and the like that are placed 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] Here, the "flow regulator" is configured as a component that can regulate the flow of a heat transfer material in an enclosed space, such as by forming a flow path, guiding the flow direction, or promoting the flow. The flow regulator is configured from multiple components, and can be configured, for example, by stacking multiple plate-like components. Furthermore, "plate-like" means that the flow regulator can be configured as a flow regulator with an overall plate-like external shape, and can also be configured as a flow regulator with an external shape that combines multiple plate-like components, such as a T-shape or a cross-shape. The multiple plate-like components can be configured by solid-state bonding to each other.

[0009] In the present invention, in the flow rectifier, the plate-like member constituting one side (herein referred to as the first plate-like member) is thicker than the plate-like member constituting the other side (herein referred to as the second plate-like member). Here, "one side" refers to the side facing the electrode tip when the flow rectifier is tilted within the sealed space when the lamp is lit, and "the other side" refers to the opposite side, or the side facing the opposite side from the electrode tip. The first plate-like member and the second plate-like member each constitute such a side.

[0010] In addition, in a discharge lamp that is another aspect of the present invention, in the rectifier, a first plate-shaped member that constitutes one side is configured to have a smaller thermal expansion coefficient than a second plate-shaped member that constitutes the other side.

[0011] In another embodiment of the discharge lamp of the present invention, the plate-shaped rectifier is composed of one member or multiple members. For example, the plate-shaped rectifier may be an integrated member having an external shape such as a T-shape or a cross shape formed by cutting or the like. When the lamp is lit, the rectifier is tilted within the sealed space, and the difference in the amount of thermal expansion along one side and the other side is suppressed. [Effects of the Invention]

[0012] According to the present invention, in an electrode, it is possible to suppress the occurrence of cracks in a flow regulator or the like that is placed in a sealed space that encloses a heat transfer body. [Brief explanation of the drawings]

[0013] [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] FIG. 3 is a schematic cross-sectional view taken along line III-III in FIG. 2. [Figure 4] FIG. 2 is a cross-sectional view of the flow regulator taken along the longitudinal direction. [Figure 5] FIG. 10 is a diagram showing a state in which the flow regulator is tilted. [Figure 6] FIG. 10 is a schematic cross-sectional view of a flow rectifier for a discharge lamp according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] 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.

[0015] 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.

[0016] 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).

[0017] Fig. 2 is a schematic cross-sectional view of the electrode (anode) 30. Fig. 3 is a schematic cross-sectional view taken along line III-III in Fig. 2.

[0018] As shown in FIG. 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 is joined to a sealing lid 60 to which an electrode support rod 17B is attached. Here, the body 34 and tip 32, excluding the sealing lid 60, are formed from the same metal material, such as tungsten. However, they may also be formed from different materials. The sealing lid 60 may also be formed from the same metal material, such as tungsten.

[0019] A cylindrical sealed space 50 is formed in the center of the interior of the body 34, coaxially with the electrode axis E. A heat transfer material M is sealed 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 to become liquid when the lamp is lit, causing convection within the sealed space 50. FIG. 2 shows the state in which the molten heat transfer material M is convecting. Here, the heat transfer material M is sealed in such a way that the entire flow rectifier 40 is immersed in the melted state of the heat transfer material M (when the lamp is lit).

[0020] A flow rectifier 40 is disposed in the sealed space 50. The flow rectifier 40 is made of a high-melting-point metal (for example, tungsten, molybdenum, tantalum, etc.) or an alloy with potassium additive, and is configured as a plate-like member having a function (structure) of promoting convection in the heat transfer body M.

[0021] Specifically, the flow straightener 40 does not have a size or shape that restricts convection in the up-down, left-right, and circumferential directions (overall circumference) of the sealed space 50. The distance D1 between the upper end 40T of the flow straightener 40 and the ceiling surface 50T of the sealed space 50, the distance D2 between the lower end 40D and the bottom surface 50B, and the distance D3 between the upper end 40T and the bottom surface 50B of the sealed space 50 and the side surface 50S of the sealed space along the direction perpendicular to the electrode axis of the sealed space 50 are ensured to allow the heat transfer material M to flow along the side surfaces 40S1 and 40S2 of the flow straightener 40 and to flow over the upper end 40T and the lower end 40D of the flow straightener 40. Note that the flow straightener 40 may be placed in the sealed space 50, in which case the distance D2 is substantially eliminated.

[0022] The flow rectifier 40 is disposed so that its central axis is aligned near the electrode axis E. However, when the heat transfer body M is molten (when the lamp is lit), the position of the flow rectifier 40 is not fixed. For this reason, the flow rectifier 40 is not shown by hatching in FIG. 2 for the sake of convenience.

[0023] Fig. 4 is a cross-sectional view of the flow regulator 40 taken along the longitudinal direction. Fig. 5 is a diagram showing the flow regulator 40 in an inclined state. The configuration of the flow regulator 40 in this embodiment will be described with reference to Figs. 4 and 5. However, in Fig. 5, the inclination of the flow regulator 40 is exaggerated.

[0024] The rectangular flow regulator 40 here has a structure in which two plate-shaped members 40A and 40B (hereinafter referred to as the first plate-shaped member and the second plate-shaped member) are stacked and joined (by welding, solid-state welding, etc.). The first and second plate-shaped members 40A and 40B are configured to have the same size (area), and can be configured, for example, with a longitudinal length L of about 30 mm and an overall thickness T of about 1 mm. Furthermore, the first and second plate-shaped members 40A and 40B are made of the same material (tungsten in this case).

[0025] On the other hand, the thicknesses T1 and T2 of the first and second plate-shaped members 40A and 40B are different, with the first plate-shaped member 40A being thicker than the second plate-shaped member 40B (T1>T2). Here, the thickness T1 of the first plate-shaped member 40A is set within the range of 1.1 to 2.0 times the thickness T2 of the second plate-shaped member.

[0026] In this way, the flow straightener 40 has a structure in which first and second plate-like members 40A and 40B of different thicknesses are laminated together, which makes it possible to suppress the occurrence of cracks in the flow straightener 40 when the lamp is tilted while it is turned on, as will be described below.

[0027] When the lamp is lit, if the rectifier 40 tilts with the side surface 40S1 of the first plate-shaped member 40A toward the electrode tip side, which becomes relatively hot, the first plate-shaped member 40A is closer to the bottom surface 50B of the sealed space 50 and therefore receives a larger amount of heat than the second plate-shaped member 40B, which is closer to the ceiling surface 50T of the sealed space 50. If it is considered that the temperature of the entire rectifier 40 rises, a temperature difference occurs between the first plate-shaped member 40A and the second plate-shaped member 40B.

[0028] However, the heat capacity between the first plate-shaped member 40A and the second plate-shaped member 40B of the flow regulator 40 differs due to the difference between the thicknesses T1 and T2. Therefore, the amount of extension of the first plate-shaped member 40A along its side surface 40S1 (longitudinal direction) due to thermal expansion (hereinafter referred to as the thermal expansion amount) becomes approximately equal to the amount of thermal expansion along the side surface 40S2 of the second plate-shaped member 40B. Alternatively, the difference in the amount of thermal expansion is suppressed. This is observed regardless of how the first plate-shaped member 40A and the second plate-shaped member 40B are joined.

[0029] Therefore, when the flow rectifier 40 is tilted, it is possible to prevent the flow rectifier 40 from warping and deforming due to the difference in the amount of thermal expansion along the side surface of the electrode tip side and the side surface of the electrode support rod side, thereby preventing cracks from occurring. As a result, the flow rectifier 40 can perform its function until the end of the lamp life, and the lamp temperature can be suppressed.

[0030] When the flow straightener 40 tilts, the relatively heavy first plate-shaped member 40A tilts toward the electrode tip, but to ensure tilting, the thickness T2 of the second plate-shaped member 40B of the flow straightener 40 may be configured to be thinner on the ceiling surface side of the sealed space 50.

[0031] Next, a discharge lamp according to a second embodiment will be described with reference to Fig. 6. In the second embodiment, a flow rectifier is formed by laminating materials having different thermal expansion coefficients.

[0032] 6 is a schematic cross-sectional view of the rectifier of the discharge lamp of the second embodiment. The rectifier 240 has a structure in which a first plate-shaped member 240A and a second plate-shaped member 240B are overlapped and joined together. The thicknesses T1 and T2 of the first plate-shaped member 240A and the second plate-shaped member 240B are equal, and the length L along the side is also equal.

[0033] On the other hand, the first plate-shaped member 240A is made of a different material from the second plate-shaped member 240B, and is made of a material with a smaller thermal expansion coefficient than the second plate-shaped member 240B. For example, the first plate-shaped member 240A is made of tungsten, and the second plate-shaped member 240B is made of molybdenum. Alternatively, the first plate-shaped member 240A may be made of tantalum, and the second plate-shaped member 240B may be made of titanium. When the flow rectifier 240 tilts, the first plate-shaped member 240A tilts toward the electrode tip.

[0034] By configuring flow regulator 240 using first plate-shaped member 240A and second plate-shaped member 240B with different thermal expansion coefficients in this way, it is possible to obtain the same effects as in the first embodiment. Even if flow regulator 240 tilts, the arrangement of flow regulator 240 or the weight of its constituent materials may be adjusted so that first plate-shaped member 240A tilts toward the electrode tip.

[0035] In the first and second embodiments, the flow regulator is configured using two plate-like members, but the flow regulator may also be configured using three or four or more stacked plate-like members. For example, in the first embodiment, the configuration may be such that plate-like members having different thicknesses are stacked, or several plate-like members may be set to the same thickness and the thickness may become thinner in stages.

[0036] In the second embodiment, the plate-like members may be stacked so that the thermal expansion coefficient increases stepwise, or several plate-like members with the same thermal expansion coefficient may be stacked so that the thermal expansion coefficient increases stepwise. Regarding the flow rectifier that is inclined while the lamp is turned on, it is sufficient to configure it so that the amount of thermal expansion along one of the opposing side surfaces (surfaces) is approximately equal to the amount of thermal expansion along the other side surface, or so that the difference in the amounts of thermal expansion is suppressed.

[0037] The above has described a flow regulator that promotes convection in the heat transfer body M, but the flow regulator may also be configured as a member that partially regulates the flow, for example, by regulating the flow in the circumferential direction of the heat transfer body M. For example, a plate-shaped flow regulator with a cross-shaped or T-shaped cross section can be configured. The thickness and thermal expansion coefficient of the portion that slopes toward the tip of the electrode, which becomes relatively hot, can be adjusted to suppress the difference in the amount of thermal expansion with other portions.

[0038] For example, when configuring a flow straightener with a T-shaped cross section, it is configured with a first plate-shaped member corresponding to the vertical bar portion of the T and a second plate-shaped member corresponding to the horizontal bar portion of the T. In this case, the first plate-shaped member configures one side surface of the T-shaped cross section flow straightener, and the second plate-shaped member configures one side surface of the T-shaped cross section flow straightener.

[0039] Then, taking into consideration the state in which the flow regulator tilts within the sealed space, it is possible to configure the first plate-shaped member to be thicker than the second plate-shaped member, or to configure the first plate-shaped member to have a smaller thermal expansion coefficient than the second plate-shaped member. Note that for a flow regulator with a T-shaped cross section, it is possible to configure the first plate-shaped member and the second plate-shaped member to fit together or to be joined together, but it is also possible to configure the cross section to be cross-shaped or T-shaped by changing the thickness through cutting or other processes. [Explanation of symbols]

[0040] 10. Discharge lamp 30 electrode (anode) 40 Flow rectifier 40A First plate-shaped member 40B Second plate-shaped member 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; In the flow rectifier, the first plate-like member constituting one side surface is thicker than the second plate-like member constituting the other side surface.

2. 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; In the flow rectifier, the first plate-like member constituting one side surface has a smaller thermal expansion coefficient than the second plate-like member constituting the other side surface.

3. 3. The discharge lamp according to claim 1, wherein the flow rectifier is formed by stacking a plurality of plate-like members.

4. 4. The discharge lamp according to claim 3, wherein the plurality of plate-like members are solid-state welded to one another.

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